harness: fix py-vs-python3 doc gap — add py.sh resolver, repoint skill/command docs

The skill/command DOCS instructed Claude to run a bare `py ...`, which is the
Windows py-launcher — absent on Linux/macOS (exit 127, hit on GURU-KALI). A blind
py->python3 swap is wrong too: python3 is a broken MS Store shim on some Windows
boxes where `py` is the correct launcher.

Fix mirrors the resolution the .sh skill scripts already do:
- New .claude/scripts/py.sh: picks the interpreter that actually RUNS —
  identity.json python.command first, then py -> python3 -> python, each
  validated with `-c 'import sys'` so the MS Store stub is skipped. exec's it.
- Repointed all DOC invocations (10 files, ~70 sites) from `py ...` to
  `bash "$CLAUDETOOLS_ROOT/.claude/scripts/py.sh" ...` (incl. the `py -c` and
  `py -` heredoc forms in checkpoint.md / mailbox.md).
- Left the .sh skill scripts untouched — they already resolve py/python/python3.
- errorlog.md: marked the GURU-KALI entry RESOLVED.

Depends on CLAUDETOOLS_ROOT (seeded by ensure-settings-env.py); py.sh also
self-resolves the repo root via git/cwd as a fallback.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

errorlog.md

@@ -9,7 +9,7 @@ Format: `YYYY-MM-DD | MACHINE | command/skill | error (brief)`
 
 <!-- Append entries below this line -->
 
-2026-06-14 | GURU-KALI | coord skill (coord.py) | Documented invocation `py .claude/skills/coord/scripts/coord.py ...` failed exit 127 — `py` (the Windows py-launcher) does not exist on Linux. Worked around with `python3`. Skill docs assume the `py` launcher; on Linux/macOS machines they need `python3`. Candidate: skill docs use a platform-neutral python resolver, or document `python3` for non-Windows.
+2026-06-14 | GURU-KALI | coord skill (coord.py) | Documented invocation `py .claude/skills/coord/scripts/coord.py ...` failed exit 127 — `py` (the Windows py-launcher) does not exist on Linux. Worked around with `python3`. [RESOLVED 2026-06-14] Added `.claude/scripts/py.sh` (resolves the working interpreter: identity.json `python.command` -> py -> python3 -> python, skipping the MS Store shim) and repointed all skill/command DOC invocations from bare `py` to `bash "$CLAUDETOOLS_ROOT/.claude/scripts/py.sh"`. The `.sh` skill scripts already resolved internally — left untouched. Broadcast to fleet.
 
 2026-06-14 | GURU-BEAST-ROG | coord skill (coord.py msg send) | `py "$CLAUDETOOLS_ROOT/.claude/skills/coord/scripts/coord.py"` failed — `$CLAUDETOOLS_ROOT` is not exported in fresh Git-bash shells here, so the path resolved under `C:\Program Files\Git\`. [RESOLVED 2026-06-14] Added `.claude/scripts/ensure-settings-env.py` (seeds `env.CLAUDETOOLS_ROOT` in per-machine `settings.local.json` from `identity.json`); Claude Code injects it into every Bash call. Wired into ONBOARDING.md + broadcast to fleet. Effective next session start.