feat: persist brainstorm decisions and have plan ingest them

[blafourcade]

Reported from AKEO enterprise framework feedback (training follow-up).

Problem to solve

The brainstorm → plan handoff has no durable contract, so locked brainstorm decisions are not guaranteed to reach the plan.

Verified in the code:

• Brainstorm produces no artifact. aidd-refine:01-brainstorm output is explicitly "No code, no plan, no files. Intent only." (plugins/aidd-refine/skills/01-brainstorm/README.md). Nothing is persisted.
• Plan does not ingest the brainstorm. aidd-dev:01-plan input is requirements (ticket URL or raw text) only — plugins/aidd-dev/skills/01-plan/actions/01-plan.md. It does not read brainstorm output.
• No "locked decision" concept. Nothing forces the plan to honor brainstorm decisions. When the plan contradicts them and later self-corrects, that is the model improvising, not a framework guarantee.

Field symptom: a plan that reopens decisions already locked during brainstorm; it sometimes catches itself, but not reliably.

Proposed solution

Make the handoff file-based and mandatory:

1. Brainstorm persists its locked decisions to a markdown artifact (e.g. aidd_docs/tasks/<yyyy_mm>/<date>-<feature>.brainstorm.md), in the same aidd_docs/tasks/ convention the plan already uses.
2. Plan accepts that artifact as an input and treats its locked decisions as constraints — flagging any conflict before generating, instead of silently diverging.

Persisting the MD alone is necessary but not sufficient: the plan must also be wired to read it, otherwise the contradiction case returns.

Content type

Skill (aidd-refine:01-brainstorm, aidd-dev:01-plan)

Target tool(s)

Claude Code

Additional context

Affected files:

• plugins/aidd-refine/skills/01-brainstorm/ (no persistence step today)
• plugins/aidd-dev/skills/01-plan/actions/01-plan.md (inputs = requirements only)

[blafourcade]

Resolved by #298 (merged).

Brainstorm-persist half — done. The "no artifact" problem is fixed: aidd-refine:01-brainstorm now consolidates the refined idea (with its settled decisions and flagged-open assumptions) and persists it to a dated file at aidd_docs/brainstorm/<yyyy_mm_dd>-<slug>.md.

Two points where this ticket's proposal was adjusted, deliberately:

• Location stays aidd_docs/brainstorm/, not aidd_docs/tasks/. A brainstorm output is intent-level, not a task artifact.
• Optional, not mandatory. finalize offers file / ticket / session and the user picks. Forcing a file on every brainstorm is wrong.

Plan-ingest half — not in scope here, moved to the plan redesign (#292). Wiring aidd-dev:01-plan to read a brainstorm artifact and treat its settled decisions as constraints belongs with the plan's input design. Carved out there so it lands with the redesign rather than bolted on.

Closing.