fix(hooks): resolve Claude plugin hook runner cross-platform

[fatkobra]

What does this PR do?

Closes #753

Summary

• update .claude-plugin/hooks/mempal-stop-hook.sh
• update .claude-plugin/hooks/mempal-precompact-hook.sh
• prefer the installed mempalace CLI
• fall back to importable python3 / python
• add execution tests for the wrapper scripts

Scope
This PR intentionally fixes the Claude plugin shell hook wrappers only.
It does not change .claude-plugin/plugin.json or .claude-plugin/.mcp.json,
which still need a separate supported mechanism for MCP command resolution.

How to test

Manual verification

• before: both wrappers failed with python3: command not found
• after: both wrappers returned {} with exit code 0 in a PATH containing python but no python3

Validation

• bash -n .claude-plugin/hooks/mempal-stop-hook.sh
• bash -n .claude-plugin/hooks/mempal-precompact-hook.sh
• ruff format tests/test_claude_plugin_hook_wrappers.py
• ruff check tests/test_claude_plugin_hook_wrappers.py
• ruff format --check tests/test_claude_plugin_hook_wrappers.py
• python -m pytest tests/test_claude_plugin_hook_wrappers.py -v
• python -m pytest tests/test_hooks_cli.py tests/test_claude_plugin_hook_wrappers.py -v
• python -m pytest tests/ -v

Checklist

• Tests pass (python -m pytest tests/ -v)
• No hardcoded paths
• Linter passes (ruff check .)

[mvalentsev]

#833 by igorls already covers this (same issue #753) -- real python resolution with MEMPAL_PYTHON override, all CI green.

Also #670, #325, #384, #410 target the same problem.

[fatkobra]

Thanks for the pointer @mvalentsev .

I checked #833, and it looks complementary rather than identical:

• fix(hooks): real python-resolution for .sh hooks, with MEMPAL_PYTHON override #833 updates the legacy shell hooks in hooks/mempal_save_hook.sh and hooks/mempal_precompact_hook.sh
• this PR updates the Claude plugin wrapper scripts in .claude-plugin/hooks/mempal-stop-hook.sh and .claude-plugin/hooks/mempal-precompact-hook.sh

Issue #753’s current code example is the wrapper path (python3 -m mempalace hook run --hook stop --harness claude-code), which is what this PR fixes.

If maintainers would prefer a single combined solution, I’m happy to close this and rework it on top of #833, but as written it looks like #942 fixes the plugin wrapper layer while #833 fixes the legacy save/precompact shell hooks.

[mvalentsev]

You're right, my mistake -- #833 targets hooks/ (legacy scripts) while this PR targets .claude-plugin/hooks/ (plugin wrappers). Different files, complementary fixes. Thanks for checking.

[mvalentsev]

btw, .codex-plugin/hooks/mempal-hook.sh has the same hardcoded python3 on line 6. Might be worth including in this PR since it's the same class of fix.

[mvalentsev]

Also worth noting: the plugin JSON configs (.claude-plugin/plugin.json, .mcp.json, .codex-plugin/plugin.json) also hardcode python3 as the MCP server command. Those need an entry point fix rather than shell fallbacks -- #805 and #340 both address that side of things.

[fatkobra]

Thanks — agreed on both points.

.codex-plugin/hooks/mempal-hook.sh does look like the same wrapper-layer issue, so I’m happy to add that here if maintainers want this PR to cover all plugin hook wrappers.

However, I think it is better to keep the MCP config files (.claude-plugin/plugin.json, .claude-plugin/.mcp.json, .codex-plugin/plugin.json) out of scope for this PR, since those seem to need the separate entry-point/config approach already being discussed in #805 / #340.