feat(v0.6): per-project detail view — branch/worktrees + active sessions

Clicking a project's name opens an in-app detail view (back button returns to
the grid) with:
- header: name, path, branch, dirty
- Branch / Worktrees: each `git worktree list` entry (branch or detached@head,
  main/current/locked/prunable tags, path) — a single-worktree repo shows its
  branch; a multi-worktree repo shows them all
- Active sessions (N): detailed rows (status, devices watching, started-ago)
  with Open + Kill
- the Claude/Codex/VS Code launcher row

Backend: src/http/worktrees.ts (parseWorktrees pure + listWorktrees via
execFile, no shell, best-effort); buildProjectDetail(cfg, path, liveSessions)
in projects.ts (validates absolute existing dir, reuses branch/dirty/session
helpers, uncached — detail is on-demand and wants fresh state); read-only
GET /projects/detail?path= (no Origin guard, like /projects; 400 missing /
404 invalid). Types: WorktreeInfo, ProjectDetail.

Frontend: detail view + navigation in projects.ts (grid<->detail), project
name becomes a link, Kill via DELETE /live-sessions/:id.

Tests +21 (452 total): worktree parser, buildProjectDetail (validation,
non-git, session merge, real git-init worktree), renderProjectDetail.
worktrees.ts 100% / projects.ts 93.8% cov. Verified in-browser: opened a
Claude session, then the detail showed its branch+worktree and the live
session with Open/Kill.

public/style.css

@@ -1156,6 +1156,160 @@ body {
   text-align: center;
 }
 
+/* ── Project detail view ─────────────────────────────────────────── */
+.proj-name-link {
+  cursor: pointer;
+}
+.proj-name-link:hover {
+  text-decoration: underline;
+  text-underline-offset: 2px;
+}
+.proj-detail-inner {
+  max-width: 900px;
+  margin: 0 auto;
+}
+.proj-back {
+  background: none;
+  border: 1px solid var(--border);
+  color: var(--text-dim);
+  border-radius: 8px;
+  padding: 6px 12px;
+  font: inherit;
+  font-size: 13px;
+  cursor: pointer;
+  margin-bottom: 16px;
+  transition: background 0.12s ease, color 0.12s ease;
+}
+.proj-back:hover {
+  background: var(--surface-2);
+  color: var(--text);
+}
+.proj-detail-head {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  flex-wrap: wrap;
+}
+.proj-detail-name {
+  margin: 0;
+  font-size: 22px;
+  font-weight: 700;
+  color: #fff;
+}
+.proj-detail-path {
+  margin: 4px 0 8px;
+  font-family: Menlo, Consolas, monospace;
+  font-size: 12px;
+  color: var(--text-faint);
+  word-break: break-all;
+}
+.proj-section-title {
+  margin: 22px 0 10px;
+  font-size: 12px;
+  font-weight: 700;
+  letter-spacing: 0.06em;
+  text-transform: uppercase;
+  color: var(--text-faint);
+}
+/* Worktrees */
+.proj-wt-list {
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+}
+.proj-wt-row {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  padding: 9px 12px;
+  background: var(--surface-2);
+  border: 1px solid var(--border);
+  border-radius: 8px;
+}
+.proj-wt-branch {
+  font-weight: 600;
+  color: var(--text);
+}
+.proj-wt-tag {
+  font-size: 10px;
+  font-weight: 700;
+  text-transform: uppercase;
+  letter-spacing: 0.04em;
+  padding: 2px 7px;
+  border-radius: 999px;
+  background: var(--surface-3);
+  color: var(--text-dim);
+}
+.proj-wt-tag-current {
+  background: var(--accent);
+  color: var(--on-accent);
+}
+.proj-wt-path {
+  margin-left: auto;
+  font-family: Menlo, Consolas, monospace;
+  font-size: 11px;
+  color: var(--text-faint);
+  word-break: break-all;
+}
+/* Detailed session rows */
+.proj-detail-sessions {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+.proj-dsession {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  padding: 10px 12px;
+  background: var(--surface-2);
+  border: 1px solid var(--border);
+  border-radius: 8px;
+}
+.proj-dsession-main {
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+  min-width: 0;
+  flex: 1;
+}
+.proj-dsession-title {
+  font-weight: 600;
+  color: var(--text);
+}
+.proj-dsession-meta {
+  font-size: 12px;
+  color: var(--text-dim);
+}
+.proj-dsession-open {
+  background: var(--accent);
+  color: var(--on-accent);
+  border: none;
+  border-radius: 7px;
+  padding: 6px 14px;
+  font: inherit;
+  font-weight: 600;
+  cursor: pointer;
+}
+.proj-dsession-open:hover {
+  background: var(--accent-2);
+}
+.proj-dsession-kill {
+  background: none;
+  border: 1px solid var(--border);
+  color: var(--text-dim);
+  border-radius: 7px;
+  width: 30px;
+  height: 30px;
+  cursor: pointer;
+  font-size: 14px;
+}
+.proj-dsession-kill:hover {
+  background: var(--red, #e5484d);
+  border-color: var(--red, #e5484d);
+  color: #fff;
+}
+
 /* Empty state */
 .proj-empty {
   color: var(--text-dim);