fix(core): harden local reliability and MCP boundaries

[jb-thery]

Summary

• make ingestion generations resumable and atomic under failures and concurrent local use
• bound and harden MCP, retrieval, local chat, TTS, cancellation, diagnostics, and access-log behavior
• add meaningful coverage gates across Core, Chat, TTS, and the landing
• align all public documentation, npm READMEs, team workflows, privacy claims, and landing SEO copy
• keep the main slogan and add the confidentiality subtagline across the requested public surfaces

Validation

• pnpm validate
• 423 tests pass: Core 348, Chat 38, TTS 26, landing 11
• Core coverage: 90.79% statements, 81.40% branches, 94.43% functions, 90.82% lines
• package checks, public API smoke, MCP smoke, release smoke, and static landing build pass
• dependency audit reports no known vulnerabilities
• import-cycle and staged secret checks pass

Release impact

Patch release for Core, Chat, and TTS. The landing is deployed separately after npm publication.

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