Session tree: simplify types, add branching API, comprehensive tests
Types:
- SessionEntryBase with type field, extended by all entry types
- CustomEntry for hooks (type: 'custom', customType, data)
- Remove XXXContent types and TreeNode (redundant)
API:
- Rename saveXXX to appendXXX with JSDoc explaining tree semantics
- Rename branchInPlace to branch() with better docs
- Add createBranchedSession(leafId) replacing index-based version
- Add getTree() returning SessionTreeNode[] for tree traversal
- Add appendCustomEntry(customType, data) for hooks
Tests:
- tree-traversal.test.ts: 28 tests covering append, getPath, getTree,
branch, branchWithSummary, createBranchedSession
- save-entry.test.ts: custom entry integration
Docs:
- Class-level JSDoc explaining append-only tree model
- Method docs explaining leaf advancement and branching
- CHANGELOG.md entry for all changes
Mario Zechner