feat: comprehensive registry improvements

Community docs:
- CODE_OF_CONDUCT.md (Contributor Covenant v2.1)
- SECURITY.md (vulnerability reporting policy)
- CHANGELOG.md (initial release notes)
- CODEOWNERS (per-type review ownership)

GitHub config:
- Issue templates: bug-report, pricing-correction, documentation
- FUNDING.yml (GitHub Sponsors)

Validation enhancements:
- Cross-reference check: hand [[requires]] → integration existence
- Routing alias collisions as warnings (errors with --strict)
- --strict flag to promote warnings to errors
- --type filter to validate single content type
- CI: add taplo format check and lychee link check jobs

Developer experience:
- Makefile with validate, fmt, and scaffold targets
- Scaffold templates for all 5 content types
- .pre-commit-config.yaml (trailing whitespace, TOML check, validate)
- docs/content-guide.md (naming, descriptions, prompts, decision guide)

Content quality:
- schema.toml: add last_verified field for model pricing
- CONTRIBUTING.md: add pricing verification guide with source links

.github/ISSUE_TEMPLATE/bug-report.yml

@@ -0,0 +1,49 @@
+name: Bug Report
+description: Report an issue with existing registry content (wrong data, broken config, etc.)
+labels: ["bug"]
+body:
+  - type: dropdown
+    id: content_type
+    attributes:
+      label: Content Type
+      description: What type of registry content has the issue?
+      options:
+        - Provider
+        - Agent
+        - Hand
+        - Integration (MCP server)
+        - Skill
+        - Plugin
+    validations:
+      required: true
+
+  - type: input
+    id: content_name
+    attributes:
+      label: Content Name
+      description: The name or ID of the affected content.
+      placeholder: e.g. openai, code-review-agent, github
+    validations:
+      required: true
+
+  - type: textarea
+    id: whats_wrong
+    attributes:
+      label: What's Wrong
+      description: Describe the issue you found.
+      placeholder: |
+        e.g. The integration command listed in the registry fails to install,
+        or the agent config references a model that doesn't exist.
+    validations:
+      required: true
+
+  - type: textarea
+    id: expected_vs_actual
+    attributes:
+      label: Expected vs Actual
+      description: What did you expect, and what actually happened?
+      placeholder: |
+        Expected: The provider config should list gpt-4o as a supported model.
+        Actual: gpt-4o is missing from the models array.
+    validations:
+      required: true