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/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