fix: use absolute default path for mdMirror fallback directory

[ScientificProgrammer]

Summary

• Fixes the mdMirror fallback directory resolving to {CWD}/memory-md instead of a stable absolute path when mdMirror.dir is not configured
• Adds getDefaultMdMirrorDir() following the same pattern as the existing getDefaultDbPath() — resolves to ~/.openclaw/memory/md-mirror
• Adds tests for the new default and config-override behavior

Closes #627

Changes

index.ts:

• Added getDefaultMdMirrorDir() helper (returns ~/.openclaw/memory/md-mirror)
• Updated createMdMirrorWriter() to use the new helper when mdMirror.dir is not set, instead of the CWD-relative "memory-md"
• Exported getDefaultMdMirrorDir for testability

test/mdmirror-fallback-dir.test.mjs (new):

• 5 test cases covering absolute path, correct default location, no legacy relative path, explicit dir override, and undefined-when-unset behavior

Testing

• All 5 new tests pass (node --test test/mdmirror-fallback-dir.test.mjs)
• test:core-regression passes
• test:storage-and-schema passes
• test:llm-clients-and-auth passes
• test:packaging-and-workflow passes
• test:cli-smoke has a pre-existing failure on master (unrelated to this change)

This PR was created with the assistance of Claude Code (AI).

[Copilot]

Pull request overview

Fixes mdMirror’s fallback directory to be a stable absolute path (under the user’s OpenClaw data dir) instead of resolving relative to the current working directory.

Changes:

• Added getDefaultMdMirrorDir() to compute ~/.openclaw/memory/md-mirror.
• Updated createMdMirrorWriter() to use the new default when mdMirror.dir is not configured.
• Added a new test file covering the default path and config override behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
index.ts	Introduces the new default mdMirror dir helper, uses it in createMdMirrorWriter, and exports it for tests.
test/mdmirror-fallback-dir.test.mjs	Adds unit tests validating the default mdMirror dir and config parsing behavior.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

The JSDoc block that describes resetRegistration() now precedes export { getDefaultMdMirrorDir };, so the comment will attach to the export statement instead of the resetRegistration function (and resetRegistration() loses its @public docs). Move the named export either above this JSDoc block, or move the JSDoc immediately above resetRegistration() (or add a separate doc comment for getDefaultMdMirrorDir if intended public).

[Copilot]

fallbackDir uses getDefaultMdMirrorDir() directly when mdMirror.dir is unset, while other default paths (e.g. dbPath) are still passed through api.resolvePath(...). For consistency (and to ensure any normalization/sandboxing logic in resolvePath is applied uniformly), consider always wrapping the chosen path with api.resolvePath, even when using the default absolute path.

Suggested change

	const fallbackDir = config.mdMirror.dir
	? api.resolvePath(config.mdMirror.dir)
	: getDefaultMdMirrorDir();
	const fallbackDir = api.resolvePath(
	config.mdMirror.dir ?? getDefaultMdMirrorDir(),
	);