Add Launcher home-screen plugin

[kasunben]

Summary

Adds plugins/launcher/ — the platform home screen (LCH-01–05) — and makes / serve the configured root plugin in place. The Launcher is the default root_plugin_id, so / and /launcher now both render the Launcher (URL stays /).

SRS: LCH-01–LCH-05, PLT-12, PLT-14, docs/plugins/launcher.md.

What's in here

The Launcher plugin — a responsive tile grid with a main section, an admin-only Admin section, and an empty state. Each tile is a plugin icon (monogram), name, and description, linking to the plugin's routePrefix.

How it gets its plugin list — the SDK boundary rule forbids a plugin importing the runtime registry, and sdk.db isn't wired until 0.5.05. So the Launcher reads a new session-gated route GET /api/plugins (forwarding the caller's cookie; middleware injects x-sovereign-user-role). Filtering is a pure selectLauncherPlugins(plugins, disabledIds, role): excludes the three chrome plugins (CHROME_PLUGIN_IDS), excludes disabled plugins, hides adminOnly plugins from non-admins.

/ serves the root plugin in place (revises the 0.4.04 redirect) — the middleware rewrites / to the configured plugin's routePrefix rather than 307-redirecting, so the URL stays /. It stays request-time and respects the configurable root_plugin_id (CON-11): a new admin-key-guarded GET /api/admin/root-plugin returns the prefix (or null when the configured plugin isn't a valid root), which the Edge middleware fetches (it can't read the DB — same pattern as the disabled-plugins check). (platform)/page.tsx keeps its redirect() as a fallback for when that fetch fails.

Sidebar — the middle monogram section now excludes chrome plugins (PLT-12); full root-plugin-first ordering (PLT-11–15) stays separate.

Notable decisions / deviations from the spec

• Components under app/_components/ (not a sibling components/) — the generate script composes only each plugin's app/ tree.
• Monogram tiles — no icon-serving pipeline yet (launcher.md Q3); matches the sidebar's monogram approach.
• /api/plugins over sdk.db — pragmatic v0.1 path; migrates to sdk.db in 0.5.05.
• In-place serve via rewrite, not redirect — keeps / as the canonical home URL while honoring configurable root.

Tests

Pure logic extracted and unit-tested; vitest.config.ts now also includes plugins/** source tests. Full suite green (101 tests).

• selectLauncherPlugins — 7 (chrome exclusion, admin vs non-admin, disabled exclusion, adminOnly flag, description default, all-chrome → empty)
• monogram — 5. These caught a real bug: the original initials || name.slice(0,2) never fell through for a single-word name (a one-letter initials is truthy), so "Tasks" would have rendered "T" not "TA", and whitespace-only names leaked spaces. Fixed.
• resolveRootRoutePrefix — 4 (valid → prefix; not-installed / disabled / admin-only → null)

format:check, lint, typecheck all green.

Verified live (real session)

Check	Result
/ (authenticated)	200 — Launcher served in place, URL stays /
/launcher (authenticated)	200, direct
/api/plugins (authenticated)	{"plugins":[]} — only chrome plugins installed
/api/admin/root-plugin (admin key)	{"routePrefix":"/launcher"}
/ and /api/plugins (no cookie)	307 → login (gated)

Not exercisable live yet: the populated grid and Admin section need a non-chrome plugin to exist (first is Tasks, a separate repo/task), and the admin path needs an admin session. Both are covered by the selectLauncherPlugins unit tests — the natural point for the browser click-through once a non-chrome plugin lands.

Versions

runtime → 0.3.0; new plugins/launcher at 0.1.0.

Draft

Marked draft pending review / browser pass.

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