Skills refinement: improve formatting, phase structure, and trigger descriptions across 9 skills

- balance-check: rewrote as explicit phases with domain routing table; expanded trigger hints
- scope-check: restructured into numbered phases for clarity
- adopt, review-all-gdds, help, project-stage-detect: add argument mode headers or trigger hints
- gate-check, sprint-status, story-readiness: minor wording and structure improvements

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

.claude/skills/gate-check/SKILL.md

@@ -1,9 +1,10 @@
 ---
 name: gate-check
-description: "Validate readiness to advance between development phases. Produces a PASS/CONCERNS/FAIL verdict with specific blockers and required artifacts."
+description: "Validate readiness to advance between development phases. Produces a PASS/CONCERNS/FAIL verdict with specific blockers and required artifacts. Use when user says 'are we ready to move to X', 'can we advance to production', 'check if we can start the next phase', 'pass the gate'."
 argument-hint: "[target-phase: systems-design | technical-setup | pre-production | production | polish | release]"
 user-invocable: true
 allowed-tools: Read, Glob, Grep, Bash, Write
+context: fork
 ---
 
 # Phase Gate Validation
@@ -33,6 +34,8 @@ The project progresses through these stages:
 
 ## 1. Parse Arguments
 
+**Target phase:** `$ARGUMENTS[0]` (blank = auto-detect current stage, then validate next transition)
+
 - **With argument**: `/gate-check production` — validate readiness for that specific phase
 - **No argument**: Auto-detect current stage using the same heuristics as
   `/project-stage-detect`, then validate the NEXT phase transition