fix(store): escape interior double-quotes in sanitizeFTS to prevent FTS5 crash

[blak0p]

🔗 Linked Issue

Closes #574

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🏷️ PR Type

• type:bug — Bug fix

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📝 Summary

• Fixes FTS5 search crash on queries containing an interior double-quote (e.g. hello"world → SQL logic error: unterminated string (1)).
• Doubles interior " inside sanitizeFTS per the FTS5 string-literal escape rule ("""), so hello"world → "hello""world".
• Adds TestSanitizeFTS with 8 cases (written first, failing per TDD; all pass after the fix).

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🔧 Changes

File	Change
internal/store/store.go	Add strings.ReplaceAll(w, \"\", \"\"\"\") after Trim in sanitizeFTS to escape interior double-quotes for FTS5.
internal/store/store_test.go	Add TestSanitizeFTS covering plain words, multiple words, single/multiple interior quotes, already-quoted, just-quotes, mixed, and empty input.

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🧪 Test Plan

• New test TestSanitizeFTS fails on unpatched code (RED) and passes after the fix (GREEN): go test ./internal/store/ -run TestSanitizeFTS -v
• Full store package passes (no regressions): go test ./internal/store/
• Built binary no longer crashes: go build -o /tmp/engram-fix ./cmd/engram && /tmp/engram-fix search 'hello"world' → clean "No memories found" (exit 0).
• Normal search still works: /tmp/engram-fix search 'sanitizeFTS' → returns results.

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✅ Contributor Checklist

• Linked an approved issue ([Bug] FTS5 search returns HTTP 500 on queries containing an interior double-quote (e.g. foo"bar) #574)
• Added exactly one type:* label (type:bug)
• Tests included with the fix
• Conventional commit format
• No Co-Authored-By trailers

Summary by CodeRabbit

• Bug Fixes
  • Improved search query handling so text containing double quotes no longer causes malformed search expressions.
  • Added coverage for quoted, mixed, and empty inputs to ensure search terms are formatted consistently.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 89c768bb-bb3d-4431-abf6-ccb447523245

📥 Commits

Reviewing files that changed from the base of the PR and between be4b613 and 9190069.

📒 Files selected for processing (2)

• internal/store/store.go
• internal/store/store_test.go

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📝 Walkthrough

Walkthrough

The sanitizeFTS function in internal/store/store.go now escapes interior double-quote characters within each token by doubling them before wrapping tokens in FTS5-quoted literals, preventing malformed MATCH queries. A new unit test validates this behavior across multiple input cases.

Changes

FTS Sanitization Fix

Layer / File(s)	Summary
Escape interior quotes in FTS sanitization internal/store/store.go, internal/store/store_test.go	sanitizeFTS doubles interior double-quote characters in each token before FTS5-quoting, and a new table-driven test (TestSanitizeFTS) validates plain words, multi-word input, quote escaping, mixed content, and empty input.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Possibly related issues

• [Bug] FTS5 search returns HTTP 500 on queries containing an interior double-quote (e.g. foo"bar) #574: This PR fixes sanitizeFTS to properly escape interior double-quotes in FTS5 queries, addressing the same underlying bug described in the issue.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main bug fix in sanitizeFTS and its FTS5 crash prevention.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

⚔️ Resolve merge conflicts

• Resolve merge conflict in branch fix/fts5-interior-quote

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