Implement Task 2 from the document-outliner-with-lsp Kiro spec.

Created comprehensive document structure operations:
- StructureOperations class with all operations
- DocumentTreeBuilder for node mapping and lookup
- promote() and demote() to adjust heading levels (1-6)
- move_up() and move_down() to reorder siblings
- nest() to move sections under new parents
- unnest() to move sections up one level
- Validation methods for all operations

Key features:
- Immutable operations (returns new Document instances)
- Node ID-based addressing (h1-0, h2-1, etc.)
- Edge case handling (level limits, boundary checks)
- Error handling with descriptive messages

Testing:
- 34 comprehensive unit tests
- Test coverage: 77.78% for operations.py
- Tests for all operations, edge cases, and immutability
- Complex scenario tests with mixed document types

All tests pass successfully.

Task: .kiro/specs/document-outliner-with-lsp/tasks.md#2
Requirements: 2.2, 2.3, 3.2, 3.3, 3.4, 3.5, 20

Implement Task 3 from the document-outliner-with-lsp Kiro spec.

Python side (JSON-RPC bridge):
- ExtensionBridge class with JSON-RPC 2.0 protocol
- Handles all document operations via stdin/stdout
- Method routing for promote, demote, move_up, move_down, nest, unnest
- Validation methods for all operations
- Comprehensive error handling and serialization
- Main entry point for standalone execution

TypeScript side (PythonBridge client):
- PythonBridge class that spawns Python process via uv
- JSON-RPC request/response handling over stdio
- Promise-based async API for all operations
- Process lifecycle management (start, stop, restart)
- Automatic restart on crash (up to 3 attempts)
- Request timeout handling (default 10s)
- Buffered line-based communication
- Convenience methods for all operations

Testing:
- 18 comprehensive integration tests
- Test coverage: 67.96% for bridge.py
- Tests for all operations (promote, demote, move_up, move_down, nest, unnest)
- Tests for validation operations
- Error handling tests (invalid JSON-RPC, unknown methods, missing params)
- Complex scenario tests (operation chains, roundtrips, reordering)
- Error recovery tests

Key features:
- Standard JSON-RPC 2.0 protocol
- Clean separation of concerns
- Type-safe TypeScript interface
- Robust error handling
- Automatic process management

All 18 tests pass successfully.

Task: .kiro/specs/document-outliner-with-lsp/tasks.md#3
Requirements: 18, 20

Implement Task 4 from the document-outliner-with-lsp Kiro spec.

VS Code Extension Components:

1. DocumentOutlineProvider (outlineProvider.ts - 230 lines):
   - Implements TreeDataProvider<OutlineNode> interface
   - Parses Markdown documents to extract heading hierarchy
   - Builds OutlineNode tree with unique IDs (h1-0, h2-1, etc.)
   - Tracks node ranges for navigation
   - Provides getTreeItem(), getChildren(), getParent() methods
   - Icons based on heading level (h1-h6)
   - Tooltips with node metadata
   - Debounced refresh mechanism (300ms)
   - Document update synchronization

2. Extension Entry Point (extension.ts - 210 lines):
   - Activates extension for Markdown files
   - Registers tree view in Explorer sidebar
   - Initializes PythonBridge for backend operations
   - Registers all commands (promote, demote, move_up, move_down, etc.)
   - Navigate to node command for clicking tree items
   - Listens for editor changes and document updates
   - Executes operations via Python bridge
   - Applies workspace edits with undo support
   - Error handling and user notifications

Testing (test_outline_integration.py - 400+ lines):
- 17 comprehensive integration tests
- All tests passing

Test categories:
- Tree building from various structures (simple, nested, complex)
- Node ID generation and uniqueness
- Mixed content with paragraphs
- Markdown parsing integration
- Operation integration (promote, demote, move)
- Edge cases (empty docs, skipped levels, reverse order)

Key features:
- ✅ Complete TreeDataProvider implementation
- ✅ Markdown parsing with heading extraction
- ✅ Hierarchical tree structure
- ✅ Unique node ID generation
- ✅ Range tracking for navigation
- ✅ Debounced refresh (300ms)
- ✅ Document synchronization
- ✅ Command integration
- ✅ Python bridge integration
- ✅ Workspace edit support
- ✅ Comprehensive testing

All 17 tests pass successfully.

Task: .kiro/specs/document-outliner-with-lsp/tasks.md#4
Requirements: 1.1, 1.2, 1.3, 1.4, 16.1, 16.2, 16.3

This commit addresses all issues identified in the Gemini Code Assist review
of PR #5 (#5 (review)).

CRITICAL FIXES:
- Fix move_up/move_down/nest operations to move entire sections (heading + content)
  instead of just heading nodes. Added get_section_range() helper method to
  DocumentTreeBuilder to identify complete sections. This prevents document corruption
  where content would end up under the wrong heading. (operations.py:70-100, 293-450)

HIGH PRIORITY FIXES:
- Implement handshake mechanism in waitForReady to avoid race conditions. Python bridge
  now prints "BRIDGE_READY" when initialized, and TypeScript waits for this signal
  before resolving the start promise. (bridge.py:313, pythonBridge.ts:348-366)

MEDIUM PRIORITY FIXES:
- Add proper TypeScript type annotations for operation methods. Created ValidationResult
  interface and updated all operation/validation methods to use OperationResult/
  ValidationResult instead of Promise<any>. Made call() method generic. (types.ts:89-97,
  pythonBridge.ts:7, 143, 183-235)

- Remove keybindings from DoctkConfiguration interface. Keybindings are contributions
  in package.json, not user-configurable settings from workspace.getConfiguration().
  (types.ts:104-115)

- Add traceback logging to error handling in bridge.py for easier debugging. Full
  traceback is now printed to stderr when exceptions occur. (bridge.py:7, 61)

- Simplify operation method signatures to return only OperationResult instead of
  redundant tuple[Document[Node], OperationResult]. Updated all callers in bridge.py
  to handle single return value. (operations.py:105, 157, 257, 348, 489, 589;
  bridge.py:107-173)

- Move local imports to top of file in operations.py. Converted TYPE_CHECKING imports
  to regular imports for better readability and to avoid hiding dependencies.
  (operations.py:3-8)

TEST UPDATES:
- Updated all LSP operation tests to handle new return signature (single OperationResult
  instead of tuple). All 34 tests now pass. (test_lsp_operations.py)

Verified with: uv run pytest tests/unit/test_lsp_operations.py -v
Result: 34 passed in 1.49s

- Remove unused imports (Optional, Node, OperationResult) from bridge.py
- Apply ruff auto-fixes for docstring formatting
- Update test_outline_integration.py tests to use new API (3 tests)

All 99 unit tests passing.

Add detailed design and implementation plan for 2 remaining PR #6 review issues:

1. CRITICAL: Granular document edits (Issue #1)
   - Added 'Optimized Edits (CRITICAL IMPROVEMENT)' section to design.md
   - Explains problem: full document replacement clears undo/redo, loses cursor
   - Solution: Backend computes ModifiedRange[], frontend applies granular edits
   - Added 5 subtasks (22.5.1-22.5.5) to tasks.md with implementation steps

2. MEDIUM: Centralize ID generation (Issue #5)
   - Added 'Centralized Node ID Generation' section to design.md
   - Explains problem: Duplicate ID logic in frontend and backend
   - Solution: Backend as single source of truth for tree structure & IDs
   - Added 4 subtasks (22.6.1-22.6.4) to tasks.md with implementation steps

Both sections include:
- Problem statement and impact
- Proposed solution with code examples
- Design rationale
- Backend and frontend changes
- Testing requirements

This provides clear roadmap for addressing the remaining architectural issues
identified in #6 (review)

Implement ModifiedRange-based edits to preserve cursor position and undo/redo
stack. This addresses the CRITICAL issue from PR #6 review.

Backend changes:
- Add ModifiedRange dataclass to protocols.py with line/column positions
- Implement DiffComputer class to compute changed text ranges
- Update all operations (promote, demote, move_up, move_down, nest, unnest)
  to return modified_ranges in addition to full document
- Update bridge.py to serialize ModifiedRange objects to JSON

Frontend changes:
- Add ModifiedRange interface to types.ts
- Update extension.ts executeOperation() to use granular edits when available
- Fall back to full document replacement if modified_ranges not provided
- This preserves cursor position and undo/redo stack

Design changes:
- Remove Approach 2 (Backend ID Service) from design.md
- Keep only Backend-Driven Tree Structure approach for centralized IDs

All 34 existing tests pass. Granular edits improve UX by:
- Preserving cursor position during operations
- Maintaining VS Code undo/redo stack
- Better performance for large documents

Related: PR #6 review issue #1 (CRITICAL)