feat(numencore-core): add handoff sections and CLAUDE.md updates to all skills

- each skill updates CLAUDE.md on completion with current phase and next step
- plan-check handoff explicitly directs user to fresh session for orchestrate
- add Edit tool to allowed-tools for CLAUDE.md management

plugins/numencore-core/skills/brainstorm/SKILL.md

@@ -2,7 +2,7 @@
 name: brainstorm
 description: Conversational design partner that helps articulate a project concept and captures it as a structured document. Use when starting a new project, feature, or idea from scratch.
 user-invocable: true
-allowed-tools: Write, AskUserQuestion
+allowed-tools: Read, Write, Edit, AskUserQuestion
 ---
 
 # Brainstorm
@@ -65,3 +65,14 @@ Unresolved items surfaced during the conversation. Known unknowns for downstream
 2. Wait for confirmation or edits.
 3. On confirmation, write `./design/concept.md` and confirm the file path.
 4. If the user requests changes, revise and present again.
+
+## Handoff
+
+On completion:
+
+1. Update `CLAUDE.md` in the project root:
+   - If it does not exist, create it.
+   - Set current phase to "brainstorm complete"
+   - Set next step to `/spec`
+   - Keep it lean — project name, one-line purpose, phase, next step, blockers.
+2. Tell the user: "Concept captured. Next step: run `/spec` to build the technical specification."

plugins/numencore-core/skills/decompose/SKILL.md

@@ -2,7 +2,7 @@
 name: decompose
 description: Break a technical specification into atomic, dispatchable task files with dependencies and context assignments. Use when spec/ exists and the project needs an implementation plan.
 user-invocable: true
-allowed-tools: Read, Write, Bash(mkdir *), Glob, AskUserQuestion
+allowed-tools: Read, Write, Edit, Bash(mkdir *), Glob, AskUserQuestion
 ---
 
 # Decompose
@@ -127,3 +127,14 @@ decomposed
 - Context files must be paths that exist in `./design/`. Do not reference files that have not been written.
 - Every component in the spec must have at least one task. Flag if a component seems to need zero tasks.
 - Zero dangling dependency references. Every ID in `depends_on` must match an existing task's `id`.
+
+## Handoff
+
+On completion:
+
+1. Update `CLAUDE.md` in the project root:
+   - Set current phase to "decomposed"
+   - Set next step to `/plan-check`
+   - Include task count and component summary
+   - Remove spec-phase details — snapshot of now only
+2. Tell the user: "Tasks decomposed. Next step: run `/plan-check` to validate the plan before implementation."

plugins/numencore-core/skills/plan-check/SKILL.md

@@ -2,7 +2,7 @@
 name: plan-check
 description: Validate decomposed task plan for dependency cycles, scope conflicts, context budget, and contract coverage. Use after /decompose and before orchestrator dispatch.
 user-invocable: true
-allowed-tools: Read, Write, Glob, Grep
+allowed-tools: Read, Write, Edit, Glob, Grep
 ---
 
 # Plan Check
@@ -116,3 +116,14 @@ Every error has: what is wrong, what breaks, how to fix it. Warnings follow the
 - Complete validation in a single pass. Either the plan passes or it does not.
 - If the plan fails, do not proceed. Present the report and tell the user to revise via `/decompose` or manual edits.
 - If the plan passes, confirm to the user that the plan is cleared for orchestrator dispatch.
+
+## Handoff
+
+On completion:
+
+1. Update `CLAUDE.md` in the project root:
+   - If pass: set current phase to "plan validated", set next step to "start a fresh session and run `/orchestrate`"
+   - If fail: set current phase to "plan check failed", set next step to "fix issues and re-run `/plan-check`", list error count
+   - Remove decompose-phase details — snapshot of now only
+2. If pass: tell the user: "Plan validated. Start a **fresh session** and run `/orchestrate` to begin implementation. A clean context window is critical for the orchestrator."
+3. If fail: tell the user: "Plan check failed. Review the errors in `./design/state/plan-check.md` and fix them, then re-run `/plan-check`."

plugins/numencore-core/skills/spec/SKILL.md

@@ -2,7 +2,7 @@
 name: spec
 description: Produce a technical specification from a brainstorm concept. Use when concept.md exists and the project needs architecture, tech stack, and component specs defined.
 user-invocable: true
-allowed-tools: Read, Write, Bash(mkdir *), Glob, AskUserQuestion
+allowed-tools: Read, Write, Edit, Bash(mkdir *), Glob, AskUserQuestion
 ---
 
 # Spec
@@ -132,3 +132,14 @@ Work through components one at a time. Present each spec to the user for review
 - Component IDs are lowercase, hyphenated (e.g., `auth-service`, `crdt-core`).
 - Every section in a component spec must have content. If genuinely not applicable, write: "Not applicable — [reason]."
 - Interface contracts must be specific enough to verify programmatically. "Exposes a REST API" is not a contract. Endpoint paths, methods, request/response shapes — that is a contract.
+
+## Handoff
+
+On completion:
+
+1. Update `CLAUDE.md` in the project root:
+   - Set current phase to "spec complete"
+   - Set next step to `/decompose`
+   - List components defined in the spec
+   - Remove any brainstorm-phase details — `CLAUDE.md` is a snapshot of now, not a log
+2. Tell the user: "Specification complete. Next step: run `/decompose` to break the spec into implementation tasks."