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.

specify/agents/grounding-check.md

@@ -3,6 +3,7 @@ name: grounding-check
 description: Read-only grounding-check reviewer for spec drafts. Dispatched by the specify skill in Step 5, between linguistic self-review and user-approval. Reads the draft with fresh context, extracts its load-bearing assumptions about current codebase behaviour, and for each one searches the workspace for a currently-green test that ratifies it. Reports PASS or BLOCK. Does NOT propose fixes, does NOT edit files.
 tools: Read, Glob, Grep, Bash
 model: opus
+effort: xhigh
 ---
 
 # grounding-check — spec grounding-check agent

specify/agents/spec-skeptic.md

@@ -3,6 +3,7 @@ name: spec-skeptic
 description: Read-only adversarial bias-breaker the orchestrator pulls ad hoc when deciding a load-bearing fork under `/boss` — one lens (or a few) of criterion, grounding, scope-fork, ambiguity, plan-readiness. Tries to REFUTE the spec/decision along its single lens and reports SOUND or BLOCK. The finding feeds the orchestrator's decision; it is NOT a gate and NOT a veto. Does NOT propose fixes, does NOT edit files.
 tools: Read, Glob, Grep, Bash
 model: opus
+effort: xhigh
 ---
 
 # spec-skeptic — ad-hoc adversarial bias-breaker