chore(scripts): add epic history rewrite tooling and SHA map docs

Replay 358 linear commits as 14 feature/fix epics with merge --no-ff;
include manifest, rewrite script, SHA map, and git-workflow-helper alignment.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/generate-commit-rewrite-map.py

@@ -0,0 +1,35 @@
+#!/usr/bin/env python3
+"""Print old->new commit SHA map by matching subject|author|email|date."""
+from __future__ import annotations
+
+import subprocess
+import sys
+
+ROOT = subprocess.check_output(["git", "rev-parse", "--show-toplevel"], text=True).strip()
+
+
+def git(*args: str) -> str:
+    return subprocess.check_output(["git", "-C", ROOT, *args], text=True).strip()
+
+
+def signature(commit: str) -> str:
+    return git("log", "-1", "--format=%s|%an|%ae|%ad", commit, "--date=iso-strict")
+
+
+def main() -> int:
+    old_hashes = git("log", "dev-old-linear", "--format=%H").splitlines()
+    new_by_sig: dict[str, str] = {}
+    for h in git("log", "dev", "--format=%H").splitlines():
+        new_by_sig[signature(h)] = h
+
+    print("old_sha\tnew_sha\tsubject")
+    for old in reversed(old_hashes):
+        sig = signature(old)
+        new = new_by_sig.get(sig, "")
+        subj = git("log", "-1", "--format=%s", old)
+        print(f"{old[:12]}\t{new[:12] if new else 'NOT_FOUND'}\t{subj}")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())