feat(manager): add interactive command center with dependency-aware recommendations

Add /gsd:manager — a single-terminal dashboard for managing milestones.
Shows all phases with visual status indicators (D/P/E columns), computes
recommended next actions, and dispatches discuss inline while plan/execute
run as background agents.

Key behaviors:
- Recommendation engine prioritizes execute > plan > discuss
- Filters parallel execute/plan when phases share dependency chains
- Independent phases (no direct or transitive dep relationship) CAN
  run in parallel — dependent phases are serialized
- Dashboard shows compact Deps column for at-a-glance dependency view
- Sliding window limits discuss to one phase at a time
- Activity detection via file mtime (5-min window) for is_active flag

New files:
- commands/gsd/manager.md — skill definition
- get-shit-done/workflows/manager.md — full workflow spec
- get-shit-done/bin/lib/init.cjs — cmdInitManager() with phase parsing,
  dependency graph traversal, and recommendation filtering
- get-shit-done/bin/gsd-tools.cjs — route 'init manager' to new command
- tests/init-manager.test.cjs — 16 tests covering status detection,
  deps, sliding window, recommendations, and edge cases

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

commands/gsd/manager.md

@@ -0,0 +1,39 @@
+---
+name: gsd:manager
+description: Interactive command center for managing multiple phases from one terminal
+allowed-tools:
+  - Read
+  - Write
+  - Bash
+  - Glob
+  - Grep
+  - AskUserQuestion
+  - Task
+---
+<objective>
+Single-terminal command center for managing a milestone. Shows a dashboard of all phases with visual status indicators, recommends optimal next actions, and dispatches work — discuss runs inline, plan/execute run as background agents.
+
+Designed for power users who want to parallelize work across phases from one terminal: discuss a phase while another plans or executes in the background.
+
+**Creates/Updates:**
+- No files created directly — dispatches to existing GSD commands via Skill() and background Task agents.
+- Reads `.planning/STATE.md`, `.planning/ROADMAP.md`, phase directories for status.
+
+**After:** User exits when done managing, or all phases complete and milestone lifecycle is suggested.
+</objective>
+
+<execution_context>
+@~/.claude/get-shit-done/workflows/manager.md
+@~/.claude/get-shit-done/references/ui-brand.md
+</execution_context>
+
+<context>
+No arguments required. Requires an active milestone with ROADMAP.md and STATE.md.
+
+Project context, phase list, dependencies, and recommendations are resolved inside the workflow using `gsd-tools.cjs init manager`. No upfront context loading needed.
+</context>
+
+<process>
+Execute the manager workflow from @~/.claude/get-shit-done/workflows/manager.md end-to-end.
+Maintain the dashboard refresh loop until the user exits or all phases complete.
+</process>