feat: add declared artifact output kinds

[sjchmiela]

Summary

Stacked on #398 (stanley/artifact-kind-registry). Until #398 lands, this draft PR includes both the artifact kind metadata commit and the declared output kinds commit; the new work is the top commit, Add declared artifact output kinds.

• Move the shared artifact wire contract into @argent/artifacts, including ArtifactHandle.
• Add declared artifacts metadata to tool definitions and expose it through tool listing metadata.
• Route tool registrations through a typed artifact registrar, so producer code registers by declared output name and the registry supplies the specific artifact kind.
• Split profiling artifact kinds into screenshot, screenshot diff/context, native trace/cpu/hangs/leaks/report, and React CPU/commits/report.

Validation

• npm run build -w @argent/artifacts && npm run build -w @argent/registry && npm run build -w @argent/tools-client
• npm run typecheck:tests -w @argent/registry && npm run typecheck:tests -w @argent/tools-client && npm run typecheck:tests -w @argent/tool-server && npm run typecheck:tests -w @argent/mcp && npm run typecheck:tests -w @argent/cli
• npm test -w @argent/tools-client -- artifacts.test.ts
• npm test -w @argent/tool-server -- artifacts.test.ts screenshot-tool.test.ts screenshot-diff-tool.test.ts android-perfetto/dispatch.test.ts ios-instruments/stop-recovery.test.ts native-profiler-analyze-failure.test.ts native-profiler-missing-trace.test.ts
• npm test -w @argent/mcp -- content.test.ts
• npm test -w @argent/cli -- run-artifacts.test.ts
• git diff --cached --check