feat(composer): discovery-phase plugin from "I want an app that..." to tracker-loaded stories

Plugin pairs with Symphony — Composer's output (issues in the project's
tracker) is Symphony's input. State-aware /composer command walks the
user through 11 phases: concept, users (with workflow probing for hidden
actors), requirements/NFR/IA, design system, interaction design, flows,
mocks, architecture, stories, roadmap, load. Each phase produces a
reviewable artifact in docs/planning/ (or, for design and interaction,
a project-local skill — see below).

Architecture is intentionally LAST, after the spec is complete. Mocks
are JSX/TSX regardless of final stack and pass a "text feasibility"
audit — every visible string is categorized (static/computed/authored),
computed strings are traced to source data, and any string implying an
unspecified feature halts the commit.

Design system and interaction design are produced as PROJECT-LOCAL
SKILLS in .claude/skills/<slug>-design-system/ and
.claude/skills/<slug>-interaction-design/, not as docs in
docs/planning/. Skills auto-load via description matching whenever UI
work happens; a reference doc gets read once and drifts out of context.
The mocks skill imports tokens directly from the design-system skill
for a single source of truth across mocks and (eventually) real code.

ui-system is currently a PLACEHOLDER — captures the minimum needed for
mocks to proceed with <TBD: ...> markers as a return-pass worklist.
Full interview specification is the next pass.

Council touchpoints baked in: PM/skeptic/end-user after requirements,
end-user/a11y after mocks, full architecture council after architecture,
plus auto-additions (legal-triage on regulated data, privacy-advocate
on PII, finance-controller on money flows).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

composer/templates/stories.md

@@ -0,0 +1,31 @@
+# Stories
+
+<!--
+Flat list ready to load into the tracker. Don't over-decompose at
+this phase — granularity shifts as the team starts working. Each
+story has acceptance criteria; the tracker is the source of truth
+once loaded, and this file becomes the local↔tracker map.
+-->
+
+## <Cluster name>
+
+### <story-id> — <Title>
+
+- **As a** <user-class>
+- **I want** <behavior>
+- **So that** <outcome>
+- **Acceptance criteria**:
+  - <observable criterion>
+  - <observable criterion>
+- **Size**: <S / M / L / XL>
+- **Depends on**: <other story-ids, if any>
+- **Mock**: <mocks/<flow>.tsx if relevant>
+- **Tracker ID**: _(filled in by /composer-load)_
+
+### <story-id> — <Title>
+
+…
+
+## <Cluster name>
+
+…