feat(lastcode): customize environment icons

[lastobelus]

The local and remote environment indicators were inconsistent across the Legacy and V2 sidebars, local rows did not reserve an icon column, and environment colors could not be customized.

This adds client-local per-environment icon colors and a local-icon toggle, reorganizes LastCode Settings into LastCode, Appearance, Environments, and Import sections, and uses absolute Monitor/Server identity across thread cards, hover details, and Legacy project groups. Semantic Default colors remain contextual; explicit colors render at full opacity. T3 settings import preserves the LastCode-only preferences.

Validation:

• pnpm lastcode:ci:quick passed on head 20cbcd7d2 after rebasing onto origin/lastcode/main at 37d746597
• 91 focused settings, import, environment-icon, and search tests passed after the rebase
• contracts, desktop, and web scoped typechecks passed
• three bounded read-only implementation review rounds completed; all findings were addressed

UI evidence:

• The approved interactive mockup remains at tmp/environment-icons-mockup.html in the author worktree and was used to confirm the requirements before implementation.
• Automated integrated capture was attempted in an isolated worktree-local T3 environment, but the collaborative preview could not reach the Vite server through its tailnet proxy (HTTP 502). No live user data was used. Manual visual checks remain requested for light/dark colors, mixed-group width, and hover targeting.

Implemented by GPT-5.6-sol through the Codex harness in T3 Code.

[lastobelus]

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Reviewed commit: 20cbcd7d24

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Codex Review: Didn't find any major issues. Keep it up!

Reviewed commit: 8ed88f580c

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".