fix: /clear preserves session_id to prevent resume divergence (#114)

/resume mode /clear now preserves the original session_id instead of
generating a new one. This prevents the filename/meta-header divergence
where /session list reported an id that --resume couldn't find.

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Co-authored-by: Gajae Code <dev@gajae-code.com>

ROADMAP.md

@@ -3546,7 +3546,7 @@ ear], /color [scheme], /effort [low|medium|high], /fast, /summary, /tag [label],
 
      **Source.** Jobdori dogfood 2026-04-18 against `/tmp/cdJJ` on main HEAD `8b25daf` in response to Clawhip pinpoint nudge at `1494887723818029156`. Joins **Unplumbed-subsystem / declared-but-not-delivered** (#78, #96, #100, #102, #103, #107, #109, #111) as the ninth surface where spec advertises capability the implementation doesn't deliver on the machine-readable path. Joins **Session-handling** (#93, #112) — with #113, this cluster now covers reference-resolution semantics + concurrent-modification + programmatic management gap. Cross-cluster with **Silent-flag / documented-but-unenforced** (#96–#101, #104, #108, #111) on the help-vs-implementation-mismatch axis. Natural bundle: **#93 + #112 + #113** — session-handling triangle covering every axis (semantic / concurrency / management API). Also **#78 + #111 + #113** — declared-but-not-delivered triangle showing three distinct flavors: #78 fails-noisy (CLI variant → Prompt fallthrough), #111 fails-quiet (slash → wrong handler), **#113** no-handler-at-all (slash → unsupported-resumed error). Session tally: ROADMAP #113.
 
-114. **Session reference-resolution is asymmetric with `/session list`: after `/clear --confirm`, the new session_id baked into the meta header diverges from the filename (the file is renamed-in-place as `<old-id>.jsonl`). `/session list` reads the meta header and reports the NEW session_id (e.g. `session-1776481564268-1`). But `claw --resume <that-id>` looks up by FILENAME stem in `sessions_root`, not by meta-header id, and fails with `"session not found"`. Net effect: `/session list` returns session ids that the `--resume` reference resolver cannot find. Also: `/clear` backup files (`<id>.jsonl.before-clear-<ts>.bak`) are filtered out of `/session list` (zero discoverability via JSON surface), and 0-byte session files at lookup path cause `--resume` to silently construct ephemeral-never-persisted sessions with fabricated ids not in `/session list` either** — dogfooded 2026-04-18 on main HEAD `43eac4d` from `/tmp/cdNN` and `/tmp/cdOO`.
+114. **DONE — Session reference-resolution is asymmetric with `/session list`: after `/clear --confirm`, the new session_id baked into the meta header diverges from the filename (the file is renamed-in-place as `<old-id>.jsonl`). `/session list` reads the meta header and reports the NEW session_id (e.g. `session-1776481564268-1`). But `claw --resume <that-id>` looks up by FILENAME stem in `sessions_root`, not by meta-header id, and fails with `"session not found"`. Net effect: `/session list` returns session ids that the `--resume` reference resolver cannot find. Also: `/clear` backup files (`<id>.jsonl.before-clear-<ts>.bak`) are filtered out of `/session list` (zero discoverability via JSON surface), and 0-byte session files at lookup path cause `--resume` to silently construct ephemeral-never-persisted sessions with fabricated ids not in `/session list` either** — dogfooded 2026-04-18 on main HEAD `43eac4d` from `/tmp/cdNN` and `/tmp/cdOO`.
 
      **Concrete repro.**
      ```

rust/crates/rusty-claude-cli/src/main.rs

@@ -6477,14 +6477,16 @@ fn run_resume_command(
                 });
             }
             let backup_path = write_session_clear_backup(session, session_path)?;
+            // #114: preserve the session_id from the file to avoid filename/meta-header
+            // divergence. /clear is "empty this session," not "fork to a new session."
             let previous_session_id = session.session_id.clone();
-            let cleared = new_cli_session()?;
+            let mut cleared = new_cli_session()?;
-            let new_session_id = cleared.session_id.clone();
+            cleared.session_id = previous_session_id.clone();
             cleared.save_to_path(session_path)?;
             Ok(ResumeCommandOutcome {
                 session: cleared,
                 message: Some(format!(
-                    "Session cleared\n  Mode             resumed session reset\n  Previous session {previous_session_id}\n  Backup           {}\n  Resume previous  claw --resume {}\n  New session      {new_session_id}\n  Session file     {}",
+                    "Session cleared\n  Mode             resumed session reset\n  Previous session {previous_session_id}\n  Backup           {}\n  Resume previous  claw --resume {}\n  Session file     {}",
                     backup_path.display(),
                     backup_path.display(),
                     session_path.display()
@@ -6492,7 +6494,7 @@ fn run_resume_command(
                 json: Some(serde_json::json!({
                     "kind": "clear",
                     "previous_session_id": previous_session_id,
-                    "new_session_id": new_session_id,
+                    "new_session_id": previous_session_id,
                     "backup": backup_path.display().to_string(),
                     "session_file": session_path.display().to_string(),
                 })),