fix: typecheck hook false positives, add 11 session-manager tests

- Fix post-edit-typecheck.js error filtering: use relative/absolute path
  matching instead of basename, preventing false positives when multiple
  files share the same name (e.g., src/utils.ts vs tests/utils.ts)
- Add writeSessionContent tests (create, overwrite, invalid path)
- Add appendSessionContent test (append to existing file)
- Add deleteSession tests (delete existing, non-existent)
- Add sessionExists tests (file, non-existent, directory)
- Add getSessionStats empty content edge case
- Add post-edit-typecheck stdout passthrough test
- Total: 391 → 402 tests, all passing

scripts/hooks/post-edit-typecheck.js

@@ -59,13 +59,21 @@ process.stdin.on("end", () => {
         } catch (err) {
           // tsc exits non-zero when there are errors — filter to edited file
           const output = (err.stdout || "") + (err.stderr || "");
+          // Compute paths that uniquely identify the edited file.
+          // tsc output uses paths relative to its cwd (the tsconfig dir),
+          // so check for the relative path, absolute path, and original path.
+          // Avoid bare basename matching — it causes false positives when
+          // multiple files share the same name (e.g., src/utils.ts vs tests/utils.ts).
+          const relPath = path.relative(dir, resolvedPath);
+          const candidates = new Set([filePath, resolvedPath, relPath]);
           const relevantLines = output
             .split("\n")
-            .filter(
-              (line) =>
-                line.includes(filePath) ||
-                line.includes(path.basename(filePath)),
-            )
+            .filter((line) => {
+              for (const candidate of candidates) {
+                if (line.includes(candidate)) return true;
+              }
+              return false;
+            })
             .slice(0, 10);
 
           if (relevantLines.length > 0) {