fix(corpflow): Sync CORPFLOW.md to the 4.0.27 contract

[ikorich]

Motivation

CORPFLOW.md targeted an older corpflow contract, so this plugin emitted handoff frontmatter the
harness rejects outright. Reproduced against handoff-harness.sh --validate-frontmatter, which
corpflow runs at every stage boundary and which hard-fails the stage:

fail: stage=DV missing required field: summary

The shape it taught (from/to/run_index/status/artifacts/metadata{}) is read by nothing:
state-patch.sh reads handoff.stage, .verdict, .summary, .worktree_path,
.worktree_branch, and handoff.metadata.* has no reader at all.

Separately, the file is read in full on every cross-plugin delegation, so its size is a
per-dispatch token cost rather than a documentation concern.

Changes

• Adopt corpflow's canonical handoff: schema. The annotated DV block is now both schema and
  template; AR, DR, SR, QA and IR collapse into a delta table.
• Add the closing elicitation sweep — required on all 13 stages, hard-failing at every stage
  boundary regardless of --strict — with its item shape, ## elicitation-sweep anchor, and rules.
• Add the state-patch.sh --facts payload, a sweep stub's only route to the gate that renders it.
• Add the worktree / worktree_path / worktree_branch fields DR checks; absent or false is
  worktree_isolation_violation.
• Correct artifact basenames: testing-N.md (was qa-<N>.md), incident-N.md (was
  incident-report.md).
• Drop needs_changes, which is outside the verdict enum.
• Mark DR, SR and QA as consultations — corpflow's own agents own those stages and artifacts — and
  state that DV ownership depends on tasks.DV0.agent.
• Correct the pipeline: nine stages by default, --secure adds SR and RE, emergency is
  IR→DV→DR→QA→RE→FN.
• Compact throughout: merge the two frontmatter sections and the return/gate-feedback sections,
  drop restated rationale. Rules that hard-fail a stage keep a short cost clause; the rest are bare
  imperatives. A size budget row is recorded in the footer.

Test plan

• Built a DV artifact from the new frontmatter block plus a matching facts.open_questions[] and
  ran corpflow's handoff-harness.sh --validate-frontmatter <artifact> --state <state.json>:
  ok: stage=DV tokens=103, exit 0. The previous shape fails the same check.
• corpflow bats suites routing-matrix, handoff-harness and desc-lint: 52 passed, 0 failed.
• scripts/validate.sh: 0 errors (1 pre-existing unrelated SKILL.md size warning).
• Section headings are byte-identical across all six sibling plugins, so a future contract change
  stays one mechanical pass.
• Compared the backticked-identifier set against the previous revision; every dropped token is one
  of the intentional removals listed above.

Notes

Part of a seven-repo sync against corpflow 4.0.27 — the template in corpflow and the five other
platform plugins carry the same change.

Closes #23