fix(prompts): hoist ToolSearch activation to top of system prompt

Smoke-7: be-dev-1 hit "Edit exists but is not enabled in this context."
Claude Code v2.1.69+ defers built-in tools (Edit, Write, Read, etc.)
behind a ToolSearch call. Weak models (minimax-m2.7) skip soft
directives buried in the briefing.

Also: 4 role prompts (developer, cell_pm, main_pm, board) claimed
"no ToolSearch needed" — a lie that compounds the problem. The
manifest registers MCP tools; built-in tools are still deferred.

Fix: compose_prompt now prepends a tool-load directive layer as the
FIRST block in the system prompt. It names the exact ToolSearch call
the role needs:
- developer/documenter: Read, Bash, Grep, Glob, Task, TodoWrite, Edit, Write
- qa/pm/board: Read, Bash, Grep, Glob, Task, TodoWrite (no Edit/Write)

The directive includes the failure mode it prevents so the model
understands what skipping the call causes.

Updated role-prompt lines that lied about ToolSearch.

7 new tests pin: directive is the first block; developer/documenter
get Edit/Write; qa/pm don't; failure-mode message is present.

agents/prompts/roles/main_pm.md

@@ -12,7 +12,7 @@ You merge what your Cell PMs submit (cell PRs into your root branch via `complet
 
 - Your `task_id` (your root coordination task) and `agent_id` are pre-baked into the gateway session.
 - Your cell-PM slugs: `be-pm`, `fe-pm`, `ux-pm`. Your team: `board`. Your channel: `main-pm-board`.
-- Your verb manifest is loaded — no `ToolSearch` needed.
+- Your verb manifest is loaded — MCP verbs are registered. Built-in tools (`Read`, `Bash`, `Task`, etc.) are deferred; run the `ToolSearch` call in the **First Action Required** block at the top of this prompt before your first read/bash.
 - Workspace: `/data/workspaces/{project}/board/main-pm/` — but you have no `Edit`/`Write` permission; this is just where merge operations resolve.
 
 ## Your verbs