fix: normalize update banner repository URLs

[Michaelyklam]

Thinking Path

• The update banner's "What's new?" link is only useful if the backend provides a canonical browser-facing repository URL.
• Issue bug: wrong link #1691 reports the link pointing at https://github.com/nesquena/hermes-webu/ instead of hermes-webui.
• The fragile part is remote URL normalization: .git must be treated as a literal suffix, not as a character set, and trailing slashes should not prevent suffix removal.
• This PR keeps the fix narrow by centralizing update remote normalization in api/updates.py and pinning the edge case with a regression test.
• The user-visible benefit is that the "What's new?" compare link stays on the intended nesquena/hermes-webui repository.

What Changed

• Added _normalize_remote_url() in api/updates.py for update-banner repository URLs.
• Preserved SSH-to-HTTPS conversion while stripping only a literal .git suffix.
• Normalized trailing slashes before and after .git removal so URLs like https://github.com/nesquena/hermes-webui.git/ become https://github.com/nesquena/hermes-webui.
• Added a regression test covering the .git/ trailing-slash case for the WebUI repo URL.

Why It Matters

The update banner should send users to the actual Hermes WebUI repository when they click "What's new?". A truncated repository slug makes the link useless and undermines the update flow at exactly the moment users are trying to understand a release.

Closes #1691.

Verification

/home/michael/.hermes/hermes-agent/venv/bin/python -m pytest tests/test_update_banner_fixes.py::TestUpdateChecker::test_repo_url_strips_dot_git_before_trailing_slashes -q
/home/michael/.hermes/hermes-agent/venv/bin/python -m pytest tests/test_update_banner_fixes.py::TestUpdateChecker -q
env -u HERMES_CONFIG_PATH -u HERMES_WEBUI_HOST /home/michael/.hermes/hermes-agent/venv/bin/python -m pytest tests/test_update_banner_fixes.py tests/test_issue1579_whats_new_link_404.py -q
env -u HERMES_CONFIG_PATH -u HERMES_WEBUI_HOST /home/michael/.hermes/hermes-agent/venv/bin/python -m pytest tests/ -q
git diff --check

Result:

RED: new regression failed before the production change because repo_url remained `https://github.com/nesquena/hermes-webui.git/`.
GREEN: TestUpdateChecker passed (3 passed in 1.42s).
Related update-banner/link tests passed (42 passed in 3.33s).
Full suite passed: 4478 passed, 2 skipped, 3 xpassed, 1 warning, 8 subtests passed in 405.72s.
git diff --check passed.

Manual verification, if applicable:

• Not applicable; this is backend URL normalization covered by regression tests.

UI media, if applicable:

• Not applicable; no visual UI layout or interaction flow changed.

Risks / Follow-ups

• Low risk: this only centralizes the existing update remote normalization and adds support for trailing slash variants.
• Follow-up only if maintainers want broader remote URL support beyond GitHub-style HTTPS/SSH origins.

Model Used

AI assisted.

• Provider: OpenAI Codex
• Model: gpt-5.5
• Notable tool use: gh issue/PR workflow, git worktree isolation, pytest regression/full-suite verification, diff inspection.

[nesquena-hermes]

Closed by the v0.51.4 release in PR #1707 (merged at 4daa238, deployed to production).

Live on production: https://github.com/nesquena/hermes-webui/releases/tag/v0.51.4

🚀