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/story-readiness/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: story-readiness
-description: "Validate that a story file is implementation-ready. Checks for embedded GDD requirements, ADR references, engine notes, clear acceptance criteria, and no open design questions. Produces READY / NEEDS WORK / BLOCKED verdict with specific gaps."
+description: "Validate that a story file is implementation-ready. Checks for embedded GDD requirements, ADR references, engine notes, clear acceptance criteria, and no open design questions. Produces READY / NEEDS WORK / BLOCKED verdict with specific gaps. Use when user says 'is this story ready', 'can I start on this story', 'is story X ready to implement'."
 argument-hint: "[story-file-path or 'all' or 'sprint']"
 user-invocable: true
 allowed-tools: Read, Glob, Grep
@@ -23,6 +23,8 @@ gap list for each non-ready story.
 
 ## 1. Parse Arguments
 
+**Scope:** `$ARGUMENTS[0]` (blank = ask user via AskUserQuestion)
+
 - **Specific path** (e.g., `/story-readiness production/epics/combat/story-001-basic-attack.md`):
   validate that single story file.
 - **`sprint`**: read the current sprint plan from `production/sprints/` (most