Remove deprecated DIFC resource API and colocate schema cache

[Copilot]

The DIFC package retained an unused deprecated resource type, while the custom-schema cache was separated from its sole production consumer.

• DIFC cleanup

  • Remove Resource, NewResource, and EmptyResource.
  • Remove tests covering the obsolete API.
  • Retain LabeledResource as the canonical resource representation.

• Configuration organization

  • Move customSchemaCache into validation_server.go.
  • Keep the shared validation file focused on the cross-file logger.

• Fixes [refactor] Semantic Function Clustering Analysis: Minor dead code and file organization findings #11649

[Copilot]

Pull request overview

Removes obsolete DIFC APIs and colocates custom-schema caching with its validator.

Changes:

• Removes deprecated Resource constructors and tests.
• Moves customSchemaCache into validation_server.go.

Show a summary per file

File	Description
internal/difc/resource.go	Removes deprecated resource API.
internal/difc/resource_test.go	Removes obsolete API tests.
internal/config/validation_shared.go	Retains only the shared logger.
internal/config/validation_server.go	Colocates the schema cache with its consumer.

Review details

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• Files reviewed: 4/4 changed files
• Comments generated: 0
• Review effort level: Balanced

[github-actions]

🔒 mcpg Read-Only Stress — default AWF

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

Part	Surface	Op	Result	Expected	Status
A1	MCP	list_issues	3 issues returned	ALLOWED	✅
A2	MCP	list_pull_requests	3 PRs returned	ALLOWED	✅
A3	MCP	get_file_contents (README.md)	content returned	ALLOWED	✅
A4	MCP	list_commits	3 commits returned	ALLOWED	✅
B	MCP	writes (reaction/star/issue/comment/branch/file/PR)	all 7 tools absent from catalog	BLOCKED	⚠️
C1	CLI	list_issues (github CLI)	3 issues returned	ALLOWED	✅
C2	CLI	get_file_contents (github CLI)	content returned	ALLOWED	✅
D	CLI	REST writes ×6	unauthenticated (no GH_TOKEN)	BLOCKED	⚠️
E	CLI	GraphQL mutations ×3	unauthenticated (no GH_TOKEN)	BLOCKED	⚠️

Overall: INCONCLUSIVE

⚠️ Part B: The github MCP bridge exposes exactly 23 read-only tools — all 7 write targets (add_issue_comment, star_repository, issue_write, create_branch, create_or_update_file, create_pull_request) are absent from the catalog. This confirms the gh-aw framework's GITHUB_READ_ONLY=1 backend defense-in-depth, but does not independently confirm mcpg's own DIFC/guard enforcement layer (write calls never reached a write-capable backend).

⚠️ Parts D & E: gh CLI is not authenticated in this environment (GH_TOKEN not set). All 9 write attempts returned "set the GH_TOKEN environment variable" — not a token-scope rejection. The REST/GraphQL write boundary could not be validated this run.

No writes leaked. All attempted reads succeeded. Gateway tool catalog is fully read-only for this runtime.

References: §32585964425

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

[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_PRs, get_file, list_commits)	data returned	ALLOWED	✅
B	MCP	writes (reaction/star/issue/comment/branch/file/PR)	all "unknown tool" — absent from catalog	BLOCKED	⚠️
C	CLI	reads (list_issues, get_file_contents)	data returned	ALLOWED	✅
D	CLI	REST writes (reaction/star/issue/comment)	gh unauthenticated (exit 4)	BLOCKED	⚠️
E	CLI	GraphQL mutations (addReaction/addStar/createIssue)	gh unauthenticated (exit 4)	BLOCKED	⚠️

Overall: INCONCLUSIVE

⚠️ Gaps noted:

• Part B: All 7 write tools absent from MCP catalog because GITHUB_READ_ONLY=1 is set unconditionally by gh-aw. Backend defense-in-depth confirmed; mcpg's own DIFC/guard layer not independently exercised on this surface.
• Parts D/E: gh CLI is not authenticated (GH_TOKEN not set in environment). All REST and GraphQL write attempts returned exit 4 (GH_TOKEN env var required). Token-scope boundary and proxy-level write-blocking could not be confirmed.

No writes succeeded. No FAIL condition triggered.

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

[github-actions]

🔒 mcpg Read-Only Stress — docker-sbx

Surface coverage: MCP tool calls + proxied CLI (REST) + GraphQL mutations
Isolation runtime: docker-sbx (KVM-isolated microVM)

Part	Surface	Op	Result	Expected	Status
A	MCP	reads (issues/PRs/file/commits)	data returned	ALLOWED	✅
B	MCP	writes (reaction/star/issue/comment/branch/file/PR)	"unknown tool" [-32602]	BLOCKED	⚠️
C	CLI	reads (list_issues, get_file_contents)	data returned	ALLOWED	✅
D	CLI	REST writes (reaction/star/issue/comment/file)	401 Bad credentials	BLOCKED	⚠️
E	CLI	GraphQL mutations (addReaction/addStar/createIssue)	401 Bad credentials	BLOCKED	⚠️

Overall: INCONCLUSIVE

• ✅ All reads succeeded (Parts A & C).
• ⚠️ Part B: All 6 write tools were absent from the MCP catalog (backend launched with GITHUB_READ_ONLY=1, so no write tools are registered). Refusals are "unknown tool" — proving backend/toolset configuration, not independent gateway DIFC enforcement. No writes leaked.
• ⚠️ Parts D & E: gh token is invalid (401 Bad credentials). All write attempts returned 401 — this is unauthenticated rejection, not evidence of gateway blocking. No writes leaked.

No writes leaked in any part. The INCONCLUSIVE designation reflects methodology gaps (no write-capable backend path reached mcpg's DIFC layer; gh unauthenticated), not a security failure.

Run: §32585964423

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