refactor: migrate claude to the target registry (no behavior change)

[steve-calvert-glean]

Summary

• Ports emitClaude/validateClaude into src/targets/claude.ts as a PluginTargetDefinition, following the pattern established in fix: correct Copilot and Antigravity plugin output + polymorphic target registry #13/refactor: migrate cursor to the target registry #14.
• Verified directly against claude plugin validate --strict: a minimal manifest with only name fails that check, confirming the existing version/description/author.name requirements already match the real CLI. No validation behavior change — this is a structural port.
• Applies the per-plugin version override in buildPluginManifest (pluginConfig.version ?? version) from the start, avoiding the bug just fixed on cursor's copy of this pattern in refactor: migrate cursor to the target registry #14 (a new regression test covers this: "applies per-target and per-plugin version overrides").
• Adds @deprecated markers to the now-superseded emitClaude/validateClaude, matching copilot/antigravity's already-migrated pattern.

Stacking

Based on refactor/cursor-target-registry (#14), since claude's resolvePluginPath/manifestPaths/marketplacePaths need the same targetConfig parameter that cursor's migration introduced on the shared interface. Merge #14 first.

Test plan

• npm run typecheck
• npm run lint
• npm test (59/59 passing, including claude's pre-existing version-override regression test)
• npm run build
• node dist/cli.js docs --check

[glean-it]

Issue: The new Claude target implementation in src/targets/claude.ts does not apply manifest override objects (pluginConfig.manifest and targetConfig.manifest) to the generated plugin and marketplace manifests, unlike the legacy claudePluginManifest and emitClaude logic in src/targets.ts, so user-specified manifest overrides will no longer take effect once the registry-based Claude target is used.

Suggested fix: Update the claude target in src/targets/claude.ts so that buildPluginManifest deep-merges the base manifest with pluginConfig.manifest and buildMarketplaceManifest deep-merges the base marketplace object with targetConfig.manifest, mirroring the existing behavior of claudePluginManifest and emitClaude in src/targets.ts (which use deepMerge(..., pluginConfig.manifest ?? {}) and deepMerge(..., targetConfig.manifest ?? {})) before calling stripUndefined.

_{🔧 Tag @ glean-for-engineering to fix or click here to fix in Glean}

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