fix(#2285): wire claude-orchestration Workflow backend into execute-phase (#2314)

The claude-orchestration capability (#1143) shipped registered 'active'
but fully inert: detectWorkflowBackend/emitWorkflowScript had no caller
outside their own CLI router, and execute-phase.md declared an
execute:wave:pre hook point that the workflow body never rendered — so
claude_orchestration.enabled:true had zero effect on real runs.

Approach B (maintainer-chosen):
- execute-phase.md now renders the execute:wave:pre hook
  (gsd_run loop render-hooks execute:wave:pre) at a new step 2.75,
  immediately before each wave's Agent() dispatch — fixing the latent
  dead-hook gap for any pre-wave capability.
- Move the claude-orchestration contribution execute:wave:post ->
  execute:wave:pre (a pre-wave backend selector belongs before dispatch,
  not after); rename fragments/execute-wave-post.md -> execute-wave-pre.md
  with prose instructing the orchestrator to call resolve-wave-dispatch
  before step 3. Unrelated wave:post contributions (ui.safety-gate, drift,
  external-job, mempalace) untouched.
- New .cts seam resolveWaveDispatch(input) composes detectWorkflowBackend
  + emitWorkflowScript into one {backend:'inline'|'workflow', ...} result;
  exposed as gsd-tools claude-orchestration resolve-wave-dispatch. This is
  a real non-CLI-router, non-test caller of both functions.

Fail-closed: any gate miss (disabled, non-Claude runtime, Workflow tool
absent, SDK below floor, execution_backend:inline, malformed input) or an
emit failure resolves to inline with a byte-identical result shape — no
regression to the default-off execute-phase path.

Regression tests (tests/fix-2285-*) cover happy-path activation + SDK-floor
BVA, the fail-closed gate-miss table with detectWorkflowBackend parity, a
fast-check composition property, capability.json contribution assertions,
and a source-contract guard that execute:wave:pre is now actually rendered.
Dependent registry-shape assertions updated in-scope.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/workflow-size-baseline.json

@@ -24,7 +24,7 @@
   "docs-update.md": 55706,
   "edit-phase.md": 12927,
   "eval-review.md": 9967,
-  "execute-phase.md": 93583,
+  "execute-phase.md": 93363,
   "execute-plan.md": 33113,
   "explore.md": 10541,
   "extract-learnings.md": 12893,