refactor: strip R6.x audit-process residue from MCP + router comments (C3)

[slin1237]

Summary

Pure comment hygiene across 11 R6.x-touched files in `crates/mcp/` and `model_gateway/src/routers/`. Mirrors C2 (#1310) which did the same for `crates/protocols/src/` after the Wave-1/2 protocol surface additions.

Rules applied

KEEP: spec references citing file/line or SDK path; per-field `///` docs; `SAFETY:` / `NOTE:` invariants; design-intent prose.

DROP: `R6.x:` task markers; per-cycle review narrative; "per coordinator" / "flagged for follow-up" / "per audit" references; "Before R6.8 this did X" historical comparisons now that the PR landed.

PRUNE: multi-paragraph doc blocks where one paragraph is signal and the rest is audit narrative.

Acceptance

```
$ grep -rnE 'R6.[0-9]' crates/mcp/src/ model_gateway/src/
(no output)

$ grep -rnE 'per coordinator|per audit|per follow-up|cycle-?[12]|Addresses.*bot-review' \
crates/mcp/src/ model_gateway/src/
(no output)
```

• No changes to any declared `pub` item, field, enum variant, `#[serde(…)]` attribute, function signature/body, test, or macro. Pure comment edits.
• `cargo check -p openai-protocol -p smg-mcp -p smg --lib --tests --benches` green.
• `cargo clippy -p openai-protocol -p smg-mcp -p smg --lib --tests --benches -- -D warnings` green.
• `cargo fmt --all` clean.

Files edited (11)

• `crates/mcp/src/transform/transformer.rs`
• `model_gateway/src/routers/common/mcp_utils.rs`
• `model_gateway/src/routers/grpc/common/responses/{streaming,utils}.rs`
• `model_gateway/src/routers/grpc/harmony/builder.rs`
• `model_gateway/src/routers/grpc/harmony/responses/{common,non_streaming,streaming}.rs`
• `model_gateway/src/routers/grpc/regular/responses/conversions.rs`
• `model_gateway/src/routers/openai/mcp/{tool_handler,tool_loop}.rs`

Net line delta: −4 lines (pruning rewrites some prose around cut lines).

Test plan

Comment-only change. Full cargo build / test / clippy / fmt verified locally.

Summary by CodeRabbit

• Documentation
  • Updated inline documentation and test comments across routing and response handling modules to remove outdated version references and reworded explanatory notes for improved clarity and consistency.

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 3eb0d91b-9900-457b-b705-e61bd4c78a6c

📥 Commits

Reviewing files that changed from the base of the PR and between 3562749 and b877928.

📒 Files selected for processing (11)

• crates/mcp/src/transform/transformer.rs
• model_gateway/src/routers/common/mcp_utils.rs
• model_gateway/src/routers/grpc/common/responses/streaming.rs
• model_gateway/src/routers/grpc/common/responses/utils.rs
• model_gateway/src/routers/grpc/harmony/builder.rs
• model_gateway/src/routers/grpc/harmony/responses/common.rs
• model_gateway/src/routers/grpc/harmony/responses/non_streaming.rs
• model_gateway/src/routers/grpc/harmony/responses/streaming.rs
• model_gateway/src/routers/grpc/regular/responses/conversions.rs
• model_gateway/src/routers/openai/mcp/tool_handler.rs
• model_gateway/src/routers/openai/mcp/tool_loop.rs

---

📝 Walkthrough

Walkthrough

This PR updates comments and documentation across multiple files, removing specific PR/release references (e.g., R6.2, R6.3, R6.4, R6.7, R6.8) and rephrasing explanatory text. No functional logic, control flow, or behavior changes are introduced.

Changes

Cohort / File(s)	Summary
MCP Transformer & Common Utils crates/mcp/src/transform/transformer.rs, model_gateway/src/routers/common/mcp_utils.rs	Updated comments removing specific PR version references (R6.2/R6.3/R6.4) and rephrased documentation about response shapes and routing behavior.
GRPC Common Responses model_gateway/src/routers/grpc/common/responses/streaming.rs, model_gateway/src/routers/grpc/common/responses/utils.rs	Removed PR/release labels and adjusted documentation for image generation handling, tool builtin wiring, and counterfactual phrasing in inline comments.
GRPC Harmony Router model_gateway/src/routers/grpc/harmony/builder.rs, model_gateway/src/routers/grpc/harmony/responses/common.rs, model_gateway/src/routers/grpc/harmony/responses/non_streaming.rs, model_gateway/src/routers/grpc/harmony/responses/streaming.rs	Removed "R6.8" and "Motivation" labels, reformatted documentation for strip_image_generation_from_request_tools and related functions.
GRPC Regular Router model_gateway/src/routers/grpc/regular/responses/conversions.rs	Removed regression label "(R6.4)" from test comment and rephrased description of image generation call handling.
OpenAI MCP Router model_gateway/src/routers/openai/mcp/tool_handler.rs, model_gateway/src/routers/openai/mcp/tool_loop.rs	Removed R6.7-specific release labels and external PR/CI log references, updated streaming tool event ordering documentation and test descriptions.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Possibly related PRs

• fix(grpc-harmony): dispatch image_generation as function tool for gpt-oss (R6.8) #1368: Updates comments and documentation explaining the image generation handling changes that were introduced in PR #1368.
• feat(openai): wire image_generation streaming events in Responses router (R6.2) #1356: Updates OpenAI router documentation referencing image generation wiring and tool event ordering behavior introduced in PR #1356.
• feat(gateway): add image_generation infrastructure for hosted-tool MCP plumbing (R6.1) #1355: Cleans up comments in the same files (transformer.rs and streaming/utils) where image generation support was initially added.

Suggested labels

mcp, model-gateway, grpc, openai

Suggested reviewers

• CatherineSue
• key4ng
• claude

Poem

🐰 Whiskers twitching, I hop through the code,
Removing old labels from every road,
R6.8, R6.7, now they must go,
Cleaner comments help our logic flow! 🌟

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: removing R6.x audit-process references from comments across MCP and router files. It is specific, concise, and clearly reflects the refactoring work described in the changeset.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch refactor/c3-r6-comment-hygiene

---

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[claude]

Clean comment-only PR — removes ephemeral R6.x / PR-number references from 11 files, making comments timeless. No logic changes. LGTM.