Add claude-profile engagement mode picker with statusline and session-start integration

- claude-profile: phase 1-3 picker (profile, mode, launch) with preset support,
  dryrun, WezTerm theming, and --append-system-prompt mode body injection
- 5 mode files (chat/quick/deep/hybrid/orch) with YAML frontmatter + prose body;
  new escalates_to field drives statusline →Opus arrow for deep and hybrid
- statusline.sh reads CLAUDE_CONFIG_DIR/active-mode.env to show
  [Sonnet→Opus] deep · topic format when launched via claude-profile
- Root CLAUDE.md session-start: auto-selects project from cwd or CLAUDE_PROJECT
  in active-mode.env, skipping the interactive picker when context is clear
- Spec, tests (37 assertions, 9 test files, all passing), context docs, and
  preset example included

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CONTEXT.md

@@ -0,0 +1,5 @@
+# Active Work
+
+<!-- Thin index — one-line entries linking to context/ detail files -->
+
+- [claude-profile engagement modes](context/claude-profile-modes.md) — Built and dryrun-tested; needs symlink install + first real `claude` launch + 5 sequenced follow-ups in FUTURE.md