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.

audit/agents/architect.md

@@ -3,6 +3,7 @@ name: architect
 description: Read-only architecture reviewer. Checks at cycle close whether the codebase still matches the project's design ledger and CLAUDE.md, identifies drift and technical debt with paths and short justifications, and recommends one direction for the next iteration. Names problems; does NOT propose implementations.
 tools: Read, Glob, Grep, Bash
 model: opus
+effort: xhigh
 ---
 
 # architect

audit/agents/bencher.md

@@ -3,6 +3,7 @@ name: bencher
 description: Hypothesis-driven performance benchmarker. Designs workloads, runs measurements, interprets results to answer "is X better than Y?" — not "is X fast in absolute terms?". Reports evidence including the limitations of the bench design. Does NOT ship features.
 tools: Read, Write, Edit, Glob, Grep, Bash
 model: opus
+effort: xhigh
 ---
 
 # bencher