fix(tier2): chdir to repo_path before state/report calls

The failcount _state_dir() and write_report _failures_dir() now default
to Path.cwd()-relative paths (scripts/tier2/state/<track>/ and
scripts/tier2/failures/ respectively, per the previous 2 commits).

run_track.py is the CLI entry point; it now does os.chdir(repo_path)
before invoking load_state/save_state/write_failure_report so the
relative paths resolve to <clone>/scripts/tier2/.

The Tier 2 agent's CWD is the clone root already, so this is a no-op
when run by the agent; it ensures the CLI works regardless of where
the user invokes it from.

Refs: conductor/tracks/tier2_no_appdata_20260618

scripts/tier2/run_track.py

@@ -7,6 +7,7 @@ itself is a thin wrapper that calls this CLI.
 from __future__ import annotations
 
 import argparse
+import os
 import subprocess
 import sys
 from datetime import datetime, timezone
@@ -74,6 +75,7 @@ def run_init(args: argparse.Namespace) -> int:
   print(f"[tier2] ERROR: git switch -c failed: {err}", file=sys.stderr)
   return 1
 
+ os.chdir(repo_path)
  state = load_state(args.track_name) if args.resume else FailcountState()
  save_state(args.track_name, state)
  started_at = datetime.now(timezone.utc)
@@ -95,6 +97,7 @@ def run_report(args: argparse.Namespace) -> int:
  repo_path = Path(args.repo_path)
  branch_name = _git_current_branch(repo_path) or f"tier2/{args.track_name}"
  started_at = datetime.now(timezone.utc)
+ os.chdir(repo_path)
  state = load_state(args.track_name)
  path = write_failure_report(
   track_name=args.track_name,