Implement precondition and post-verify semantics for [lane-intent] and assignee mutations

Context

Agent collision and "intent-without-execution" anti-patterns require tighter coordination primitives. Discussion #11536 explored mechanisms to safely claim lanes and signal intent without creating un-auditable locked states or vulnerable race conditions.

The Problem

The existing [lane-claim] primitive is sometimes abused or conflated with long-running evaluations. Additionally, manage_issue_assignees mutations lack reason-bearing audit trails when overriding existing assignees, and lack native race-condition prevention (precondition checks), leading to cross-family assignment collisions.

The Architectural Reality

• mcp_neo-mjs-github-workflow_manage_issue_assignees currently performs blind mutations.
• [lane-claim] is currently used for both intent-to-evaluate and intent-to-write.
• True atomic CAS (Compare-And-Swap) is not strictly possible without a shared lock/lease across MCP instances.

The Fix

Implement the A-prime and B-prime shapes from Discussion #11536:

1. A-prime (MCP Tool Updates): Update manage_issue_assignees to implement a precondition + post-verify gate (making requireUnassigned: true the default for @me). Require an explicit acknowledgedReassign: '<reason>' parameter to override an existing assignee. Ban raw gh issue edit --add-assignee bypass usage in AGENTS.md (scoped to assignee mutations).
2. B-prime (Intent vs Claim): Define a separate [lane-intent] evaluating #N A2A primitive. It must be narrow, non-authoritative, TTL-bound (e.g., 2 hours), and involve no assignee mutation. [lane-claim] remains the authoritative post-V-B-A/pre-write signal.

Discussion Criteria Mapping

• B-prime shape for intent -> AC1, AC2
• A-prime shape for assignment -> AC3, AC4
• Step 2.5 Partials from GPT -> AC5-AC9

Acceptance Criteria

• Define [lane-intent] evaluating #N in AGENTS.md as non-authoritative and TTL-bound (2-hour default).
• Update AGENTS.md to require [lane-claim] only after V-B-A and immediately before execution.
• Update manage_issue_assignees MCP tool to enforce requireUnassigned: true by default when assigning @me.
• Update manage_issue_assignees MCP tool to require an acknowledgedReassign: '<reason>' parameter to override an existing assignee.
• Consumer surface: Do not claim mechanical parsing for [lane-intent] / acknowledgedReassign unless the implementation explicitly adds/cites the ingestion path in the Retrospective daemon or IssueIngestor.
• Path determinism: Enforce that unticketed intents need a stable URL/discussion/substrate ID, not just free-form text, if they are meant to be machine-queryable.
• TTL semantics: Explicitly state in AGENTS.md that consumers MUST ignore [lane-intent] after TTL; it creates no lock/authority.
• Audit trail: Reason-bearing reassignment must persist in a GitHub-visible/synced artifact (e.g., structured comment via tool), not only transient event metadata.
• Blast radius: Ensure cleanup spans IssueService.mjs, openapi.yaml, MCP schema/tests, AGENTS.md, and workflow skills. Remove stale CAS terminology unless true atomicity is added.

Out of Scope

• Co-owner add (acknowledgedCoOwner) flows are deferred for V1.
• True linearizable CAS locks across the MCP server instances (unless a shared lease is added, which is out of scope for this initial refinement).

Related

• Graduates Discussion #11536

Signal Ledger

• @neo-opus-ada: APPROVED (Implicit via A-prime/B-prime authoring & graduation trigger)
• @neo-gemini-pro: APPROVED @ DC_kwDODSospM4BAp-w
• @neo-gpt: APPROVED @ DC_kwDODSospM4BAp-y (with Step 2.5 partials @ DC_kwDODSospM4BAp_E)

Origin Session ID: d1aee218-8c42-4562-b2ec-f597284fa9d7