Per-dispatch variety-stamp completeness (#1028: #865 enforce + #891 templates + #873 feature-stamp)

[michael-wojcik]

Closes the #1028 umbrella as one work-unit: dispatch-boundary enforcement (#865),
plan-mode/rePACT template parity + resolver-inherit fail-safe (#891), and
feature-task variety-stamp (#873).

• Enforcement (Enforce orchestrator-side metadata.variety stamp on Task B dispatches (currently advisory-only) #865): deterministic STRONG-WARN at the dispatch wiring write in
  handoff_ordering_gate.py, keyed on is_pact_specialist_owner agentType resolution
  (replaces the dead owner.startswith("pact-") predicate). Env-gated DENY via
  PACT_DISPATCH_VARIETY_MODE (default warn, fail-open except a precise deny match).
  Surgical split: missing-stamp enforcement at the boundary; malformed-when-present
  stays a PostToolUse advisory.
• Template parity (plan-mode consultation Task B omits per-dispatch variety stamp → reasoning_reconstruction band unresolvable #891): the 4-rationale variety block added to plan-mode.md and
  rePACT.md dispatch templates; _resolve_required_band_via_blocks inherits the
  parent variety.total when a child task is unstamped (singleton-blocks and
  parent-stamped guarded, fail-open otherwise).
• Feature-stamp (Extend variety-stamp enforcement to umbrella/feature tasks (for computable feature-vs-dispatch divergence) #873): comPACT.md stamps the feature task's variety.total.
• Tests: non-mocked deny-honor seam probe + fail-open-on-crash + perf-guard,
  both-modes-matrix, malformed-type. Full suite GREEN (9567 passed, 0 errors).

Version: 4.4.41 (PATCH).

Closes #891
Closes #873
Completes the enforcement ACs of #865; closure of #865 and the #1028 umbrella
pending the optional post-merge deny-honor runtime probe.