fix(search): let cancelled live reads stop instead of reporting partial coverage

[waleedlatif1]

Summary

• A cancelled or timed-out live read could resolve as a successful, partially covered document. readDiscussionSection turns every per-section failure into a "could not be fully retrieved" warning, including the caller's abort, so Drive, Linear, and GitHub reads kept going after Stop, a cancelled MCP request, or the 15s read budget
• readLiveDocument now decides cancellation by the signal's state right after the provider read (signal.throwIfAborted(), before verifyCurrent), as search already does. That covers every abort reason: Copilot Stop's string reasons, custom abort errors, an MCP cancel reason, AbortError, and TimeoutError, on every provider path. Genuine provider failures still degrade to partial coverage
• Notion: a notion-ai-search result without a type is reported as partial instead of complete; an explicit workspace_search fallback stays complete
• Linear: backwards (oldest-first) reads validate hasPreviousPage, the flag they actually page on
• Meeting content and discussion entries are cut with truncateAtCodePoint, so a cut never splits a surrogate pair and the discussion cap is exact

Type of Change

• Bug fix

Testing

• readLiveDocument rejects with the exact reason for a string reason, AbortError, and TimeoutError during a Drive discussion read, and a connection reset on the comments request still returns the document with the coverage warning
• Notion missing-type → partial; Linear backwards read without hasPreviousPage → rejected
• With staging's sources swapped in, all five new cases fail
• lib/sim-search suites (303 tests), type-check, lint, and check:audits pass

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated
docs	Skipped		Sep 28, 2026 1:29am UTC

[cubic-dev-ai]

No issues found across 9 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Re-trigger cubic}

[greptile-apps]

Confidence Score: 5/5

[Medium risk] Fixes cancellation handling in live document reads.

The PR appears safe to merge; no outstanding finding or new actionable issue was identified.

Summary

The PR makes cancelled live reads reject rather than return partial coverage, improves coverage reporting and pagination validation, and avoids splitting Unicode characters when truncating content. The change since the previous review adds a cancellation check after current-scope verification. The earlier cancellation finding is fixed.

_{Reviews (2) · Last reviewed commit: "fix(search): stop a live read cancelled ..."}

[waleedlatif1]

@greptile

[waleedlatif1]

@cubic-dev-ai review this PR

[cubic-dev-ai]

@cubic-dev-ai review this PR

@waleedlatif1 I have started the AI code review. It will take a few minutes to complete.

[cubic-dev-ai]

No issues found across 9 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Re-trigger cubic}