feat: add per-mode theme overrides

[aneym]

Summary

[theme.custom] applies one set of overrides in both modes, so with auto_switch a value tuned for the dark theme washes out when the light theme activates. #837 proposed per-mode blocks and @ogulcancelik approved a PR there.

This adds [theme.custom.light] and [theme.custom.dark]. Resolution order: theme defaults, then [theme.custom], then the block matching the resolved appearance. Configs that do not use the new blocks resolve exactly as they do today.

[theme]
auto_switch = true

[theme.custom]
accent = "#fe640b"

[theme.custom.light]
text = "#2e3145"
subtext0 = "#494c66"

Both panes are the same seeded layout rendered with catppuccin-latte active; the only difference is the [theme.custom.light] block.

Refs #837. #2032 asks for the same capability from a full-theme-pair angle; this shape covers it through [theme.custom.light]/[theme.custom.dark] alone.

Test plan

• Branch rebased onto current master (93e0086). just check steps all pass: fmt, clippy, windows-lint, config-reference parity, integration assets, plugin marketplace, script unittests
• nextest: 3046 tests, 3043 passed. The 3 failures (live_handoff x2, api_ping pane-info) are pty-timing timeouts that fail identically on unmodified master in the same environment
• New tests in src/config/theme.rs cover parsing both blocks, per-mode resolution precedence, and that configs without the new blocks resolve unchanged
• Ran it locally for several days with auto_switch flipping between catppuccin-mocha and catppuccin-latte

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 70f69ba7-0176-4bcf-abe3-b47ddf3cbe8a

📥 Commits

Reviewing files that changed from the base of the PR and between d1a4e65 and baff68f.

📒 Files selected for processing (4)

• docs/next/website/src/data/config-reference.json
• src/app/mod.rs
• src/app/state.rs
• src/config/theme.rs

🚧 Files skipped from review as they are similar to previous changes (4)

• docs/next/website/src/data/config-reference.json
• src/config/theme.rs
• src/app/mod.rs
• src/app/state.rs

---

📝 Walkthrough

Walkthrough

The theme configuration now supports light- and dark-appearance custom color overrides. Automatic theme switching applies active mode overrides after shared custom and legacy accent colors. Tests and documentation cover the new behavior.

Changes

Theme appearance overrides

Layer / File(s)	Summary
Theme configuration contract src/config/theme.rs, src/config.rs	CustomThemeColors defines optional light and dark ModeThemeColors tables. Deserialization tests cover their color values. The type is publicly re-exported.
Mode-aware palette resolution src/app/state.rs, src/app/mod.rs	Automatic theme selection passes active mode overrides to palette resolution. Palette::with_mode_overrides applies token values after shared custom and legacy accent colors. Tests verify precedence and fallback behavior.
Configuration documentation and examples docs/next/website/src/content/docs/configuration.mdx, docs/next/website/src/data/config-reference.json, src/main.rs	Documentation, reference data, and default examples describe light and dark appearance-specific color settings.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant HostAppearance
  participant resolve_effective_theme
  participant resolve_palette_for_theme_name
  participant Palette
  HostAppearance->>resolve_effective_theme: select light or dark appearance
  resolve_effective_theme->>resolve_palette_for_theme_name: pass active mode overrides
  resolve_palette_for_theme_name->>Palette: apply shared custom colors
  Palette->>Palette: apply active mode-specific colors

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Possibly related PRs

• herdrdev/herdr#2488: Both changes modify theme configuration and palette handling, but this change adds appearance-specific color overrides while that PR validates unknown theme names.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: adding per-mode theme overrides.
Description check	✅ Passed	The description directly explains the new light and dark theme override blocks, resolution order, compatibility, and tests.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

_{Comment @coderabbitai help to get the list of available commands.}

[kangal-bot]

Hi @aneym, thanks for your interest in contributing!

Herdr automatically admits focused bug fixes from contributors who are not maintainers when the title uses fix: ... or fix(scope): ... and the patch changes no more than 20 files and 1,000 total added or deleted lines.

Contributors who are not maintainers may submit only focused bug fixes. If this pull request fixes a bug, rename it to use a conventional fix: ... or fix(scope): ... title, then tag a maintainer to review and reopen it.

Feature requests, behavior changes, and other proposals belong in GitHub Discussions and require maintainer approval before a pull request.

If this gate classified the pull request incorrectly, reply and tag a maintainer listed in .github/MAINTAINERS. A verified maintainer can reopen it; reopening by anyone else will be closed again automatically.

Patch size: 7 changed files, 391 changed lines.

See https://github.com/herdrdev/herdr/blob/master/CONTRIBUTING.md for the contribution policy.

[greptile-apps]

Greptile Summary

The PR adds light- and dark-specific custom palette overrides used when automatic theme switching is enabled.

• Adds nested [theme.custom.light] and [theme.custom.dark] configuration models and reference documentation.
• Resolves the active mode override after built-in and shared custom colors.
• Adds parsing and palette-resolution coverage for the new configuration.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
src/config/theme.rs	Adds deserializable light and dark color override blocks with parsing coverage.
src/app/mod.rs	Selects and applies the resolved appearance-specific override after shared palette customization.
src/app/state.rs	Adds token-by-token application of appearance-specific palette overrides.
docs/next/website/src/data/config-reference.json	Documents every supported light and dark override key.
docs/next/website/src/content/docs/configuration.mdx	Documents the new blocks and their resolution precedence.

_{Reviews (3): Last reviewed commit: "feat: add per-mode theme overrides" | Re-trigger Greptile}

[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

src/config/theme.rs (1)

126-146: 🗄️ Data Integrity & Integration | 🟠 Major | ⚡ Quick win

Add sidebar_bg to mode-specific overrides.

ModeThemeColors omits sidebar_bg, although CustomThemeColors and Palette support it. A user cannot set a light-only or dark-only sidebar background.

Add sidebar_bg to ModeThemeColors. Apply it in Palette::with_mode_overrides. Add parsing and palette-resolution coverage.

Proposed fix

--- a/src/config/theme.rs
+++ b/src/config/theme.rs
 pub struct ModeThemeColors {
     pub accent: Option<String>,
     pub panel_bg: Option<String>,
+    pub sidebar_bg: Option<String>,
     pub surface0: Option<String>,

--- a/src/app/state.rs
+++ b/src/app/state.rs
         if let Some(c) = &custom.panel_bg {
             self.panel_bg = parse_color(c);
         }
+        if let Some(c) = &custom.sidebar_bg {
+            self.sidebar_bg = parse_color(c);
+        }

Based on supplied downstream context, src/app/state.rs:641-692 has the same omission.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 1cefb19c-6dd0-416f-9a93-164b72966a75

📥 Commits

Reviewing files that changed from the base of the PR and between 66ee3b8 and d1a4e65.

📒 Files selected for processing (7)

• docs/next/website/src/content/docs/configuration.mdx
• docs/next/website/src/data/config-reference.json
• src/app/mod.rs
• src/app/state.rs
• src/config.rs
• src/config/theme.rs
• src/main.rs

🚧 Files skipped from review as they are similar to previous changes (6)

• docs/next/website/src/content/docs/configuration.mdx
• docs/next/website/src/data/config-reference.json
• src/main.rs
• src/app/state.rs
• src/app/mod.rs
• src/config.rs

[aneym]

Added sidebar_bg to the per-mode overrides in baff68f: field on ModeThemeColors, applied in with_mode_overrides, covered in the parse and palette-resolution tests, and documented under theme.custom.light/theme.custom.dark in the config reference.