fix(plugin): derive missing crystallization summaries

[RerankerGuo]

Description

Fixes #2143.

When the crystallization LLM returns a structurally useful draft but omits
summary, normalization currently produces an empty string and the default
validator rejects the entire draft.

This change derives a sanitized fallback summary in this order:

1. retrieval_blurb / retrievalBlurb, when provided by older or alternate models
2. The first normalized step body or title
3. The normalized display title or skill name
4. A final static fallback

Existing non-empty summaries are unchanged. Missing steps remain invalid, so
this does not weaken the structural validator.

Related Issue (Required): Fixes #2143

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• Unit Test
• Test Script Or Test Steps

Evidence:

• Before the fix, the two new regressions failed with
  skill.crystallize.invalid: missing summary.
• npm test -- tests/unit/skill/crystallize.test.ts -> 9 passed.
• npm run lint -> TypeScript project check passed.
• npm run build -> plugin build passed.
• The broader tests/unit/skill run passed 35 tests; 13 database-backed tests
  could not start because the local Node 26 install lacks the
  better-sqlite3 native binding after an --ignore-scripts install.

Impact

• Breaking change: no
• Scope: skill draft normalization only
• Dependencies: none
• Existing valid summaries and validation of missing steps are unchanged

Checklist

• I have performed a self-review of my own code
• I have added tests that prove the fix is effective
• I have linked the issue to this PR
• No documentation update is required for this internal recovery path
• Review requested from @hijzy and @whipser030

Reviewer Checklist

• closes crystallize: defaultDraftValidator throws skill.crystallize.invalid: missing summary when LLM omits summary field #2143
• Made sure Checks passed
• Tests have been provided

[Memtensor-AI]

🤖 Open Code Review

Target: PR #2222
Task: afc7396792f82328
Base: main
Head: fix/issue-2143-crystallize-summary-fallback

🔍 OpenCodeReview found 1 issue(s) in this PR.

---

1. apps/memos-local-plugin/core/skill/crystallize.ts (L367)

The hardcoded magic number 200 in summarySource.slice(0, 200) should be extracted to a named constant. This makes the intent clear and makes it easier to update the limit in one place if needed.

Suggested fix:

const MAX_SUMMARY_LENGTH = 200;
// ...
const summary = summarySource.slice(0, MAX_SUMMARY_LENGTH);

💡 Suggested Change

Before:

  const summary = summarySource.slice(0, 200);

After:

const MAX_SUMMARY_LENGTH = 200;
// ...
  const summary = summarySource.slice(0, MAX_SUMMARY_LENGTH);

Generated by cloud-assistant via Open Code Review.

[Memtensor-AI]

✅ Automated Test Results: PASSED

All tests passed (9/9 executed). memos_local_plugin/unit: 9/9. Duration: 3s [advisory, non-gating] AI-generated tests on branch test/auto-gen-32083f8dbbd21f66-20260805162117: 19/19 passed — these do NOT affect the PR verdict; review the branch manually.

Branch: fix/issue-2143-crystallize-summary-fallback

[syzsunshine219]

Updated this PR at a1dcfb2c to address both unresolved OCR findings.

Changes:

• select the first sanitized summary source, then apply the 200-character cap uniformly to explicit and derived summaries
• remove the unreachable optional/static fallback; displayTitle is already guaranteed non-empty
• add a regression test for an explicit 250-character summary (observed failing before the fix, passing after)

Merge status:

• the PR is already based on the latest main (0 behind / 1 ahead)
• merge-tree completed without conflicts

Local verification:

• focused crystallization suite: 10/10 passed
• complete local-plugin suite: 159 files, 1305 passed, 2 skipped
• npm run lint: passed
• npm run build: passed
• git diff --check: passed

Fresh OCR and AutoTest checks are pending. Python Actions run: https://github.com/MemTensor/MemOS/actions/runs/31122705498 (16 jobs queued while GitHub Actions is under a major outage).

[Memtensor-AI]

✅ Automated Test Results: PASSED

All tests passed (10/10 executed). memos_local_plugin/unit: 10/10. Duration: 3s [advisory, non-gating] AI-generated tests on branch test/auto-gen-afc7396792f82328-20260807012102: 24/25 passed, 1 failed — these do NOT affect the PR verdict; review the branch manually.

Branch: fix/issue-2143-crystallize-summary-fallback