Add repository implementation for comment CRUD and thread queries.
Handles PostgreSQL-specific operations including array marshaling for langs
field and proper NULL handling for optional JSON fields.

Key operations:
- Create/Update/Delete with soft delete support
- GetByURI with ErrCommentNotFound for missing records
- ListByRoot/ListByParent for thread traversal
- ListByCommenter for user history
- CountByParent for pagination

All queries filter out soft-deleted comments (deleted_at IS NULL).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Define core comment domain model and repository interface for AppView indexing.
Comment entity tracks threading references (root/parent), soft delete state,
and denormalized reply count.

Repository interface provides:
- CRUD operations (Create, GetByURI, Update, Delete)
- Thread queries (ListByRoot, ListByParent, CountByParent)
- User queries (ListByCommenter)

Designed for read-heavy workload with denormalized counts for performance.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Add PostgreSQL schema for comment indexing from Jetstream firehose.
Supports threaded discussions with root/parent references, soft deletes,
and denormalized counts (reply_count on comments, comment_count on posts).

Key features:
- Composite indexes for efficient thread queries
- Soft delete preserving thread structure
- Out-of-order event handling via denormalized counts
- GIN index on content for future full-text search

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Add convenient shell script for validating all lexicon schemas and test data.

**Added:**
- scripts/validate-schemas.sh - Wrapper around cmd/validate-lexicon

**Usage:**
```bash
./scripts/validate-schemas.sh
```

**Features:**
- Validates all 58 lexicon schema files
- Validates cross-references between schemas
- Tests all lexicon test data files (15 valid, 11 invalid)
- Reports test coverage per record type

This script makes it easy to verify lexicon changes before committing,
addressing the PR review requirement for lexicon validation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Remove test data files that are no longer valid after enum → knownValues changes:

**Removed obsolete enum validation tests:**
- post/post-invalid-enum-type.json - knownValues allow unknown types
- community/moderator-invalid-permissions.json - knownValues allow extension
- interaction/share-valid*.json (2 files) - interaction lexicons removed
- interaction/tag-*.json (3 files) - interaction lexicons removed

**Fixed invalid test data:**
- moderation/tribunal-vote-valid.json - corrected invalid AT-URI format
Changed: at://$1/... → at://did:plc:testuser123/...

**Rationale:**
With knownValues (vs strict enums), the lexicon validator accepts unknown
values for extensibility. These test files expected rejection of unknown
enum values, which no longer applies under the knownValues pattern.

**Validation Status:** All 58 lexicons validated successfully
- 15/15 valid test files passing
- 11/11 invalid test files correctly rejected
- 13 record types with test coverage

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Apply comprehensive atProto Lexinomicon best practices to all lexicon schemas:

**Extensibility (16 enum → knownValues changes):**
- Convert all closed enums to knownValues for federation compatibility
- Affected fields: sort, timeframe, postType, vote, blockedBy, embedType
- Allows unknown values from other implementations gracefully
- Enables future additions without breaking existing clients

**Internationalization (11+ maxGraphemes additions):**
- Add maxGraphemes constraints to all string fields with maxLength
- Ensures proper UTF-8 multi-byte character handling
- Affected: community names, descriptions, alt text, edit notes, titles, content
- Follows 10-20 byte-to-grapheme ratio for international text

**Schema Organization (3 reference fixes):**
- Fix feed references: getTimeline#feedViewPost → defs#feedViewPost
- Fix community references: list#communityView → defs#communityView
- Remove unimplemented aspectRatio reference from video.json
- Centralizes definitions in defs.json files per best practices

**Files Modified:**
- embed: external.json, images.json, video.json
- feed: getAll.json, getCommunity.json, getDiscover.json, getTimeline.json
- community: defs.json, profile.json, search.json
- community/post: get.json, search.json, update.json

**Impact:** No breaking changes - existing code uses defensive validation patterns
that work seamlessly with knownValues. All validation tests passing.

References: https://github.com/bluesky-social/atproto/discussions/4245

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>