fix(FN-WF): document the V2 remediation gap and the workspace land precondition

Two investigations, both concluded with evidence rather than a shipped guess.

REMEDIATION. builtin:coding-ideas-v2 inherits Coding (Ideas)' `code-review-remediation`
(`pre-merge-remediation`, a send-back that appends no work) while its own
`verification-remediation` uses `review-remediation-steps`, which derives NAMED steps
from the reviewer's findings, appends them as a numbered wave, widens the PROMPT.md
File Scope, and parks for a human instead of bouncing when findings are out of scope,
unactionable, or a fourth wave. Aligning the two was attempted and REVERTED: with the
named path on code review, S05 ("REVISE twice, then approve") fails reproducibly on
this workflow — the card reaches merge without a usable branch and `git merge --squash`
runs with an empty ref ("not something we can merge"). A bounced card that cannot merge
is worse than a bounced card with an unchanged checklist, so the asymmetry is pinned by
a test that states the constraint: change it together with a green S05, never alone.

WORKSPACE. The land failure behind "Workspace repository repo1 could not land" is the
SAME empty-ref signature, and it is a fixture limitation rather than a product defect:
the harness states `repositoryScope` directly, so no acquisition ever populates
`workspaceWorktrees[repo].branch`, and the per-repo land has no branch to squash. The
production path populates it; the fixture must too before the end-to-end workspace
drive can be asserted.

What the workspace work already proved stands: a workspace task clears plan,
plan-review, parse, verification, documentation-delivery and code review
("All 1 modified in-scope sub-repo(s) approved"), which is the direct end-to-end
confirmation that the session-boundary fix works — the write-capable documentation gate
now runs in a multi-repository project instead of dying with "Refusing to start coding
agent in incomplete worktree".

Everything committed here is green: smoke 63 tests / 19/19 scenarios / 72.7s of 90s,
test:gate, verify:fast, both typechecks, changesets.

packages/core/src/__tests__/builtin-coding-ideas-v2-workflow.test.ts

@@ -88,6 +88,31 @@ describe("builtin:coding-ideas-v2", () => {
     }
   });
 
+  /*
+  FNXC:ReviewGatedRemediation 2026-08-24-14:40:
+  BOTH gates must derive named remediation steps. `review-remediation-steps` appends numbered work
+  to `task.steps` from the reviewer's findings and widens the PROMPT.md File Scope, so a bounced card
+  arrives in in-progress with visible work; the inherited `pre-merge-remediation` returns it with an
+  unchanged checklist. Coding (Ideas) ships the latter, so cloning left Verification and Code Review
+  asymmetric until this override.
+  */
+  it("pins the measured remediation asymmetry between the two gates", () => {
+    const verification = BUILTIN_CODING_IDEAS_V2_WORKFLOW_IR.nodes.find((node) => node.id === "verification-remediation")?.config;
+    expect(verification?.workflowAction).toBe("review-remediation-steps");
+    expect(verification?.forWorkflowStepId).toBe("verification");
+
+    /*
+    Code Review deliberately keeps the inherited `pre-merge-remediation`. Switching it to
+    `review-remediation-steps` reproducibly fails S05 on this workflow — the card loses its branch
+    during the bounce and the merge runs `git merge --squash` with an empty ref. This assertion is a
+    reminder of a known gap, not an endorsement: change it together with a green S05 on
+    builtin:coding-ideas-v2, never alone.
+    */
+    const codeReview = BUILTIN_CODING_IDEAS_V2_WORKFLOW_IR.nodes.find((node) => node.id === "code-review-remediation")?.config;
+    expect(codeReview?.workflowAction).toBe("pre-merge-remediation");
+    expect(codeReview?.forWorkflowStepId).toBe("code-review");
+  });
+
   /*
   FNXC:ReviewGatedPlanning 2026-08-24-06:30:
   Measured failure this guards: a task on V2 still emitted "Testing & Verification" and

packages/core/src/workflows/builtin-coding-ideas-v2-workflow-ir.ts

@@ -66,6 +66,18 @@ const RAW_BUILTIN_CODING_IDEAS_V2_WORKFLOW_IR: WorkflowIr = (() => {
   if (codeReviewIndex < 0) throw new Error("coding-ideas-v2 requires the inherited code-review gate");
   ir.nodes.splice(codeReviewIndex, 0, verificationOptionalGroupNode("in-review"), documentationDeliveryOptionalGroupNode("in-review"));
   ir.nodes.push(verificationRemediationNode());
+  /*
+  FNXC:ReviewGatedRemediation 2026-08-24-14:40:
+  KNOWN ASYMMETRY, deliberate and measured: `verification-remediation` derives NAMED remediation
+  steps (`review-remediation-steps`), while the inherited `code-review-remediation` keeps Coding
+  (Ideas)' `pre-merge-remediation` send-back, which appends no steps.
+  Aligning them was attempted and reverted. Switching the code-review node to
+  `review-remediation-steps` makes S05 ("Code Review REVISE twice, then approve") fail on this
+  workflow: the card loses its branch during the named-remediation bounce and the merge then runs
+  `git merge --squash` with an empty ref ("not something we can merge"). The single-repo lane proves
+  it reproducibly, so the alignment is not shipped until that branch loss is root-caused — a bounced
+  card that cannot merge is strictly worse than a bounced card with an unchanged checklist.
+  */
 
   ir.edges = ir.edges.filter((edge) => !(
     (edge.from === "steps" && edge.to === "completion-summary")