docs: remove Wails/desktop instructions that do not exist

[vsolano9]

Description

guide.md still describes a Wails native app, a ui/ React/Next.js frontend, and an eko ui command. None of those exist on main. .github/SUPPORT.md links here, so a new user following the first install path hits cd: ui: No such file or directory and then unknown command "ui".

This keeps the CLI walkthrough (init / save / summary / history / restore), which still matches the binary, and replaces the three fictional build options with go build -o eko .. A pointer to docs/docs/cli-reference.md covers the commands the old guide never mentioned (diff, tag, clean, migrate, completion, eko ai).

Related Issues

Resolves #66

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring / Code quality improvement

Technical Details & Architecture Notes

Verified against origin/main at ec12094:

• git ls-tree has .github, Formula, assets, cmd, deploy, docs, internal. No ui/, no wails.json.
• rootCmd registers ai, clean, completion, diff, history, init, migrate, restore, save, summary, tag. No ui.
• The only remaining "Wails" mention in the tree after this change is a leftover comment in .gitignore, which this PR leaves alone.

How Has This Been Tested?

• Built go build -o eko . from this branch. eko ui exits 1 with unknown command "ui" for "eko".
• test ! -d ui is true.
• go test ./... — all packages with tests pass (cmd, internal/ai, internal/api, internal/db, internal/manifest, internal/notify, internal/objects, internal/snapshot, internal/util). Same result as clean main.

The Vercel check is the known fork-authorization failure (Authorization required to deploy). It is unrelated to this docs change; previous merged PRs from this fork had the same check.

Checklist

• My code follows the style guidelines of this project (run gofmt and go vet)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (including README.md and CONTRIBUTING.md)
• My changes generate no new compiler or linter warnings
• I have added/updated unit tests that prove my fix is effective or that my feature works
• All new and existing unit tests pass locally with my changes

[vercel]

@vsolano9 is attempting to deploy a commit to the Kavindu's projects Team on Vercel.

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