fix(openclaw-migration): case-preserving brand rewrite + one-time ~/.openclaw residue banner (#16327)

Two related fixes for OpenClaw-residue problems after an OpenClaw→Hermes
migration (especially migrations done via OpenClaw's own tool, which
doesn't archive the source directory).

1. optional-skills/migration/openclaw-migration/scripts/openclaw_to_hermes.py:
   rebrand_text() was rewriting ~/.openclaw/config.yaml → ~/.Hermes/config.yaml
   (capital H — a directory that doesn't exist). Now case-preserving:
   "OpenClaw" → "Hermes" (prose), but "openclaw" → "hermes" (so filesystem
   paths land on the real Hermes home). Regex logic unchanged — replacement
   function now checks if the matched text was all-lowercase and emits the
   replacement in the matching case.

2. agent/onboarding.py + cli.py: one-time startup banner the first time
   Hermes launches and finds ~/.openclaw/. Tells the user to run
   `hermes claw cleanup` to archive it, gated on the existing onboarding
   seen-flag framework (onboarding.seen.openclaw_residue_cleanup in
   config.yaml). Fires once per install; re-running requires wiping that
   flag or running cleanup directly.

Tests:
- 4 new TestDetectOpenclawResidue tests (present / absent / file-instead-
  of-dir / default-home smoke)
- 2 TestOpenclawResidueHint tests (content check)
- 2 TestOpenclawResidueSeenFlag tests (flag isolation + round-trip)
- test_rebrand_text_preserves_filesystem_path_casing regression test
  with 4 scenarios including the exact ~/.openclaw/config.yaml case
- Existing test_rebrand_text_* tests updated to the new case-preserving
  contract (lowercase input → lowercase output)

Co-authored-by: teknium1 <teknium@noreply.github.com>

cli.py

@@ -9073,6 +9073,30 @@ class HermesCLI:
             _welcome_text = "Welcome to Hermes Agent! Type your message or /help for commands."
             _welcome_color = "#FFF8DC"
         self._console_print(f"[{_welcome_color}]{_welcome_text}[/]")
+        # First-time OpenClaw-residue banner — fires once if ~/.openclaw/ exists
+        # after an OpenClaw→Hermes migration (especially migrations done by
+        # OpenClaw's own tool, which doesn't archive the source directory).
+        try:
+            from agent.onboarding import (
+                OPENCLAW_RESIDUE_FLAG,
+                detect_openclaw_residue,
+                is_seen,
+                mark_seen,
+                openclaw_residue_hint_cli,
+            )
+            if not is_seen(self.config, OPENCLAW_RESIDUE_FLAG) and detect_openclaw_residue():
+                try:
+                    _resid_color = _welcome_skin.get_color("banner_dim", "#B8860B")
+                except Exception:
+                    _resid_color = "#B8860B"
+                self._console_print(f"[{_resid_color}]{openclaw_residue_hint_cli()}[/]")
+                try:
+                    from hermes_cli.config import get_config_path as _get_cfg_path_resid
+                    mark_seen(_get_cfg_path_resid(), OPENCLAW_RESIDUE_FLAG)
+                except Exception:
+                    pass  # best-effort — banner will fire again next session
+        except Exception:
+            pass  # banner is non-critical — never break startup
         # Show a random tip to help users discover features
         try:
             from hermes_cli.tips import get_random_tip