Drop github-workflow comment tools' shared-account-era identity byline

Context

Operator surfaced (2026-06-15, alongside #13365) that the github-workflow MCP comment tools inject a "special comment formatting" agent-identity byline that dates from when Gemini posted via the operator's shared tobiu GitHub account — the body had to stamp the real author because the gh account didn't identify the agent. Now every named maintainer posts from its OWN dedicated gh identity (@neo-opus-ada, @neo-gpt, …), so the injected byline duplicates the gh-account author — the same redundancy #13365 removes from PR bodies, one layer down at the tool level.

The Problem

manage_issue_comment (and likely siblings) takes an agent param described as "Automatically formats the comment with the agent's identity" (openapi.yaml:409, param at :450 — format [Model Name] ([Agent Wrapper])). When the posting gh account already IS the agent (@neo-*), this byline is redundant noise on every comment, and it forces every call-site to pass + maintain the agent string (extra surface + drift risk).

The Architectural Reality

• ai/mcp/server/github-workflow/toolService.mjs:405: manage_issue_comment binds to IssueService.manageIssueComment — the byline formatting lives in that service.
• ai/mcp/server/github-workflow/openapi.yaml:409 (the auto-format claim) + :450 / :1419 (the agent param, "[Model Name] ([Agent Wrapper])").
• Sibling write tools to audit for the same injection: manage_pr_review, create_issue, manage_issue_labels, manage_pr_reviewers.
• Distinct + out of scope: toolService.mjs already has a write-IDENTITY GUARD (fail-closed drift assertion, :213+) — that GUARD stays; only the redundant byline FORMATTING is in scope.
• Sibling convention change: #13365 / PR #13367 trims the PR-body @handle for the identical reason (the gh account identifies the agent).

The Fix

1. Analyze which github-workflow tools inject an agent-identity byline (start: IssueService.manageIssueComment + the agent param across the openapi).
2. Where the posting gh account is the agent's own dedicated identity (the normal case), drop the injected byline — the gh-account author IS the attribution. Make the agent param optional/removable.
3. Keep an explicit attribution ONLY for any path that still posts via a shared / non-agent account (the cross-harness analogue of #13365's Model-A/Model-B case). If no such path remains, remove the injection outright.
4. Update the openapi tool descriptions (drop the "Automatically formats… identity" claim) + any call-sites that pass agent.

Contract Ledger Matrix

Decision Record impact

aligned-with the #13365 authorship-trim convention. No ADR governs the tool byline.

Out of Scope

• The PR-body authorship convention — that is #13365 / PR #13367 (this is the tool-layer counterpart).
• The write-identity GUARD (fail-closed drift assertion) — stays; only the redundant byline FORMATTING is in scope.

Acceptance Criteria

• github-workflow comment/write tools no longer inject a redundant agent-identity byline when the posting account is the agent's own gh identity.
• The agent param is optional (or removed), required only on a shared-account path if one remains.
• openapi descriptions drop the "Automatically formats… with the agent's identity" claim where it no longer applies.
• The write-identity guard is unaffected (audited, not touched).

Live latest-open sweep: checked latest 15 open issues at 2026-06-15T~16:54Z; no equivalent github-workflow-formatting ticket (nearest is #13365, the PR-body counterpart, + #13352 gh-auth, both distinct). A2A in-flight: no [lane-claim] on this scope.

Origin Session ID: 73156d71-9a96-4bf1-bbc8-d6487ca7dddd

Retrieval Hint: "github-workflow MCP comment tool agent identity byline shared tobiu account redundant manage_issue_comment"

Authored by Ada (Claude Opus 4.8, Claude Code). Session 73156d71-9a96-4bf1-bbc8-d6487ca7dddd.