feat(agents): pin explicit reasoning effort on every agent and workflow call

Effort joins model as a mandatory pin: an omitted field inherits the
session effort, coupling every dispatch's thinking budget to whatever
the user happens to be chatting at (often xhigh) — the same
session-state coupling the model pin removes. The assignment follows
the model split:

- xhigh on every opus agent (judgement roles are the pipeline's
  quality floor and must not degrade with the session);
- high on every sonnet agent (tightly-scoped plan execution gains
  little from xhigh but pays its latency per dispatch, and these are
  the per-task in-loop roles — wall-clock is the efficiency metric;
  not lower than high, since re-loops cost more than saved thinking);
- medium inline in the workflow scripts for schema-bound
  extraction/verification stages that author no code (preflight,
  plan-extract, mini-verify, tree-check, finalize, build/suite
  verify).

Workflow agent() calls pass effort explicitly on every call — whether
frontmatter effort propagates through an agentType dispatch is
undocumented, so the scripts do not rely on it. Policy documented in
docs/agent-template.md § effort, mirroring § model.

implement/agents/implementer.md

@@ -3,6 +3,7 @@ name: implementer
 description: Carries out a tightly scoped implementation task. Reads the task extract handed by the controller, implements, builds, tests, reports a structured status with the diff. NOT for architecture decisions, NOT for self-curated scope; this agent executes a plan that has already been made.
 tools: Read, Edit, Write, Bash, Glob, Grep
 model: sonnet
+effort: high
 ---
 
 # implementer

implement/agents/quality-reviewer.md

@@ -3,6 +3,7 @@ name: quality-reviewer
 description: Read-only code-quality reviewer for project diffs. Reports Strengths, Issues by severity (Important / Minor / Nit), and a Recommendation. Runs after spec-reviewer is green; spec-compliance is NOT this agent's concern. Does NOT propose fixes.
 tools: Read, Glob, Grep, Bash
 model: opus
+effort: xhigh
 ---
 
 # quality-reviewer

implement/agents/spec-reviewer.md

@@ -3,6 +3,7 @@ name: spec-reviewer
 description: Read-only spec-compliance reviewer. Compares a recent diff against the task text from a plan under docs/plans handed by the controller. Reports missing requirements and unrequested extras. Does NOT review code quality (that is quality-reviewer's job) and does NOT propose fixes (the implementer fixes; the orchestrator coordinates).
 tools: Read, Glob, Grep, Bash
 model: sonnet
+effort: high
 ---
 
 # spec-reviewer

implement/agents/tester.md

@@ -3,6 +3,7 @@ name: tester
 description: Writes new fixtures and E2E tests after a cycle or feature ships. Verifies a feature works from build through to observable output. Each test protects a named property; tests check observable behaviour, not implementation internals.
 tools: Read, Edit, Write, Bash, Glob, Grep
 model: sonnet
+effort: high
 ---
 
 # tester