feat(search): add typed projected result outputs

[SamMorrowDrums]

Summary

Adds typed inputs, compact output schemas, and protocol-gated structured results for seven search and repository-list read tools while preserving their legacy text output.

Why

This is the next migration layer in the typed-schema stack, making modern clients able to consume validated structured outputs without changing older-client behavior.
Fixes N/A — this stack layer has no linked issue.

What changed

• Migrated search_code, search_issues, search_pull_requests, list_issues, list_pull_requests, list_branches, and list_tags to the typed registration path.
• Added compact typed output DTOs that honor requested fields projections; retained existing text serializers, scope policies, error handling, and IFC labels.
• Added input normalization for legacy enum casing and numeric-string pagination, and removed the obsolete raw field_filters parser.
• Added protocol wire, output-schema conformance, projection, and compatibility tests. Tool input schemas were unchanged, so existing toolsnap snapshots remain valid; script/generate-docs produced no documentation diff.

MCP impact

• No tool or API changes
• Tool schema or behavior changed
  Modern protocol clients receive output schemas and structured content for the seven migrated tools. Legacy/unknown clients retain their existing text output and behavior.
• New tool added

Prompts tested (tool changes only)

• “Search GitHub code for main.go and return only the name field.” — exercised search_code with fields: ["name"] and verified text/structured output match.
• “List tags in owner/repo.” — exercised list_tags and verified legacy text and modern structured output.
• Output schemas for all seven tools were resolved and validated against representative output values in TestTypedProjectedReadToolOutputSchemas.

Security / limits

• No security or limits impact
• Auth / permissions considered
  Existing scope access declarations were preserved.
• Data exposure, filtering, or token/size limits considered
  Structured DTOs remain compact and respect each tool’s existing fields selection; IFC labeling and sanitization paths are preserved.

Tool renaming

• I am renaming tools as part of this PR (e.g. as a part of a consolidation effort)
  • I have added the new tool aliases in deprecated_tool_aliases.go
• I am not renaming tools as part of this PR

Note: if you're renaming tools, you must add the tool aliases. For more information on how to do so, please refer to the official docs.

Lint & tests

• Linted locally with ./script/lint
• Tested locally with ./script/test

./script/lint ran but reports three govet diagnostics on unchanged parent-stack code: pkg/github/discussions.go:102:24, pkg/github/discussions.go:103:24, and pkg/lockdown/lockdown_test.go:92:70, each inline: cannot inline: type parameter inference is not yet supported. Compatible checks passed with ./bin/golangci-lint run --disable govet (0 issues). ./script/test passed. Focused tests passed with go test ./pkg/github -run '^(TestTypedProjectedReadTool(OutputSchemas|OutputsRespectFieldSelection)|TestNormalizeTypedReadArgumentsPreservesLegacyValues|Test_SearchCode|Test_SearchIssues|Test_ListIssues|Test_ListPullRequests|Test_SearchPullRequests|Test_ListBranches|Test_ListTags)$' -count=1. script/generate-docs passed with no generated documentation changes. CI was still pending at the last check; the PR remains draft.

Docs

• Not needed
• Updated (README / docs / examples)

script/generate-docs completed successfully; it produced no changes because the input tool documentation did not change.

[github-actions]

⚠️ License files need updating

The license files are out of date. I tried to fix them automatically but don't have permission to push to this branch.

Please run:

script/licenses
git add third-party-licenses.*.md third-party/
git commit -m "chore: regenerate license files"
git push

Alternatively, enable "Allow edits by maintainers" in the PR settings so I can fix it automatically.

[Copilot]

Copilot review overview

🟡 Changes recommended

Structured issue results lose meaningful empty field_values, and most inferred item schemas lack representative validation.

Review effort: Balanced
Findings: 1 · 1

Open (2)

• Preserve empty field_values in structured search results · New
• Add representative items to search response schema samples · New

What changed in this PR

Adds typed, protocol-gated structured outputs to seven search and repository-list tools while retaining legacy text responses.

Changes:

• Adds typed inputs, projected output DTOs, and compatibility normalization.
• Gates output schemas and structured content by protocol version.
• Adds projection/schema tests and regenerates license reports.

File	Description
pkg/​github/​search.go	Types search_code input and output.
pkg/​github/​search_utils.go	Types shared issue/PR search handling.
pkg/​github/​issues.go	Types issue search/list projections.
pkg/​github/​pullrequests.go	Types PR search/list projections.
pkg/​github/​repositories.go	Types branch and tag outputs.
pkg/​github/​typed_read_normalizers.go	Normalizes legacy typed arguments.
pkg/​github/​typed_search_outputs_test.go	Tests schemas, protocol gating, and projections.
third-party-licenses.linux.md	Consolidates Linux architecture licenses.
third-party-licenses.windows.md	Consolidates Windows architecture licenses.

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