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/adr/0000-template.md

@@ -0,0 +1,50 @@
+# ADR-NNNN — <Title>
+
+- **Status**: proposed | accepted | superseded by ADR-MMMM | deprecated
+- **Date**: YYYY-MM-DD
+- **Deciders**: <names / handles>
+
+## Context
+
+<!--
+What's forcing this decision. Pull constraints from requirements.md,
+nfr.md, ia.md, interaction-design.md. Two or three short paragraphs.
+-->
+
+## Decision
+
+<!--
+One sentence. The thing we are doing.
+-->
+
+We will …
+
+## Alternatives considered
+
+<!--
+Each one with one paragraph: what it was, why we didn't pick it.
+-->
+
+### <Alternative A>
+
+<why we didn't pick this>
+
+### <Alternative B>
+
+<why we didn't pick this>
+
+## Consequences
+
+<!--
+What changes because of this decision. Positive AND negative. The
+negative list is the more important one.
+-->
+
+**Positive**:
+- <…>
+
+**Negative / accepted costs**:
+- <…>
+
+**Open follow-ups**:
+- <thing this decision implies we now have to figure out later>