feat(v0.6): show CLAUDE.md on the project detail page + /init generate/update button

The detail page now reads <repo>/CLAUDE.md and shows it in a scrollable
monospace box, with one smart button: "↻ Update" when it exists / "✨ Generate"
when it doesn't. The button opens an interactive Claude session in the repo
running /init (claude "/init") so you review what it writes — reuses the project
launcher, no new backend orchestration, stays a byte-shuttle.

- ProjectDetail += hasClaudeMd / claudeMd; buildProjectDetail reads CLAUDE.md
  (truncated 64KB, best-effort, in the existing Promise.all)
- renderProjectDetail: CLAUDE.md section (content box or empty state) + button
- style.css: .proj-section-row / .proj-claudemd-btn / .proj-claudemd

Tests +5 (458): backend read present/absent; frontend content+Update,
empty+Generate, button opens `claude "/init"`. Verified: tsc clean, full suite
green, build OK, curl returns the content, in-browser shows the box + button.

src/types.ts

@@ -244,6 +244,8 @@ export interface ProjectDetail {
   dirty?: boolean;
   worktrees: WorktreeInfo[]; // empty for a non-git dir
   sessions: ProjectSessionRef[]; // running sessions under this path (fresh)
+  hasClaudeMd: boolean; // a CLAUDE.md exists at the project root
+  claudeMd?: string; // its content (truncated for display) when present
 }
 
 export interface SessionManager {