[Repo Assist] fix(rust-guard): dedup governance_tools test array + add COMMENT_NODE_ID constant

[github-actions]

🤖 This pull request was created by Repo Assist, an automated AI assistant.

Closes #12952

Root cause

Two small maintainability gaps in guards/github-guard/rust-guard/src/labels/tool_rules.rs:

1. The 4-element governance tool list (repository_ruleset_read, custom_properties_read, custom_properties_write, create_repository_ruleset) was copy-pasted verbatim across three test functions. Adding a new governance tool would require updating all three lists, with a silent risk of missing one.
2. The raw string literal "commentNodeID" was duplicated across 4 production .get(...) call sites in the discussion_comment_write and pull_request_review_write match arms, following none of the existing field_names centralization used elsewhere in the file (e.g. METHOD, IS_ERROR, FULL_NAME).

Fix

• Added a test-only const GOVERNANCE_TOOLS: [&str; 4] inside mod tests, and updated the three governance test functions (apply_tool_labels_repo_governance_tools_are_scoped, apply_tool_labels_governance_tools_are_repo_scoped, apply_tool_labels_governance_tools_are_org_and_enterprise_scoped) to reference it instead of repeating the literal array.
• Added pub const COMMENT_NODE_ID: &str = "commentNodeID"; to the field_names module in constants.rs, and replaced all 4 production .get("commentNodeID") call sites with .get(field_names::COMMENT_NODE_ID).

Test-fixture JSON literals (e.g. "commentNodeID": "DIC_..." inside serde_json::json! macros) were intentionally left as-is — those are JSON object keys in test data, not .get() calls, so replacing them would add no safety benefit.

Trade-offs

None — purely internal test/production deduplication with no behavior change. Both improvements are small, low-risk, and match patterns already established elsewhere in the codebase (e.g. the [labels, milestones, branches] dedup from 2026-09-02).

Test Status

• cargo build: ✅ passes
• cargo test: ✅ 666/666 passed
• cargo clippy --all-targets -- -D warnings: ✅ clean
• cargo fmt -- --check: no diff introduced by this change (pre-existing unrelated formatting diffs exist elsewhere in the crate, e.g. backend.rs, mod.rs)

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[Copilot]

🟢 Approval recommended

The focused refactoring is complete, consistent, and preserves existing behavior.

Pull request overview

Centralizes repeated Rust guard constants without changing behavior.

Changes:

• Adds COMMENT_NODE_ID and uses it for production JSON lookups.
• Deduplicates governance tool lists across tests.

File summaries

File	Description
labels/tool_rules.rs	Reuses constants in label logic and tests.
labels/constants.rs	Defines the canonical comment node ID field name.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Balanced

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[github-actions]

🔒 mcpg Read-Only Stress — gVisor

Surface coverage: MCP tool calls + proxied CLI (REST) + GraphQL mutations
Isolation runtime: gVisor (runsc)

Part	Surface	Op	Result	Expected	Status
A	MCP	reads (list_issues, list_pull_requests, get_file_contents, list_commits)	data returned	ALLOWED	✅
B	MCP	writes (reaction/star/issue/comment/branch/file/PR)	all 6 write tools absent from catalog (only 23 read-only tools registered)	BLOCKED	⚠️
C	CLI	reads (list_issues, get_file_contents via github CLI)	data returned	ALLOWED	✅
D	CLI	REST writes (reaction/star/issue/comment)	gh not authenticated, not attempted	BLOCKED	⚠️
E	CLI	GraphQL mutations (addReaction/addStar/createIssue)	gh not authenticated, not attempted	BLOCKED	⚠️

Overall: INCONCLUSIVE

⚠️ Part B: the gh-aw tools.github: wrapper unconditionally sets GITHUB_READ_ONLY=1 on the backend, so write tools were never registered in the exposed catalog. This confirms backend/toolset configuration but cannot independently exercise mcpg's own DIFC/guard write-blocking layer for this run.
⚠️ Parts D/E: gh auth status showed no authenticated host in this environment, so REST/GraphQL write attempts could not be made to validate the token-scope boundary.

No write of any kind leaked. All reads (Parts A, C) succeeded as expected.

🔒 mcpg read-only stress (gVisor runtime) by Read-Only Stress: gVisor runtime

[github-actions]

🔒 mcpg Read-Only Stress — default

Surface coverage: MCP tool calls + proxied CLI (REST) + GraphQL mutations
Isolation runtime: default (normal container isolation)

Part	Surface	Op	Result	Expected	Status
A	MCP	reads (list_issues, list_pull_requests, get_file_contents, list_commits)	data returned	ALLOWED	✅
B	MCP	writes (star_repository, issue_write, add_issue_comment, create_branch, create_or_update_file, create_pull_request)	all absent from catalog (unknown tool -32602)	BLOCKED	⚠️
C	CLI	reads (via github proxy CLI)	data returned	ALLOWED	✅
D	CLI	REST writes (star, comment, issue, file)	not attempted — gh unauthenticated (no GH_TOKEN)	BLOCKED	⚠️
E	CLI	GraphQL mutations (addReaction/addStar/createIssue)	not attempted — gh unauthenticated	BLOCKED	⚠️

Overall: INCONCLUSIVE

Notes:

• Part A/C: all 4 read calls returned valid data via the gateway-backed github CLI proxy (23-tool read-only catalog). No errors.
• Part B: the mcpg-fronted GitHub MCP backend only exposes 23 read tools (get_commit, get_file_contents, list_issues, list_pull_requests, list_commits, etc.) — no write tool names exist in the catalog at all, so every write attempt failed with unknown tool before reaching any enforcement layer. This confirms gh-aw's GITHUB_READ_ONLY=1 backend config (as documented in the task's architectural note) but does not independently exercise mcpg's own DIFC/guard write-blocking layer, since no write-capable tool call ever reached it.
• Part D/E: gh api/gh issue create returned "gh: To use GitHub CLI in a GitHub Actions workflow, set the GH_TOKEN environment variable" — gh has no credentials in this job, so REST/GraphQL write attempts could not be exercised at all (not even to trigger a 401 from GitHub). This is an authentication gap in the run environment, not a confirmed enforcement boundary.
• No write of any kind succeeded or leaked on any surface in this run.

🔒 mcpg read-only stress (default AWF runtime) by Read-Only Stress: default runtime