feat(langgraph): observe readonly interrupt batches

[blove]

The private LangGraph runtime reported paused outcomes but discarded pending interrupt payloads. It now exposes the complete readonly interrupt batch in the same immutable snapshot as messages and application values, so Angular and React can observe live pauses and restore them from explicit history loads.

A pure projector preserves SDK payloads and metadata, accumulates separate dynamic batches, deduplicates IDs, and restores all latest checkpoint tasks. Empty __interrupt__ envelopes correctly represent static breakpoints. All three snapshot candidates are owned before publication, with reentrant ownership checks and existing recovery correlation preserved. Stop retains observed interrupts; accepting a new submission clears them.

Core and native observer implementations are unchanged. This remains a private adapter milestone: no resume command, extra I/O, schema validation, nested interrupt routing, or public package cutover. Follows merged #1118.

Verification

• 359 runtime tests across 15 files; strict runtime type probes and LangGraph lint (0 errors, 68 existing warnings).
• Four foundation packages: tests, type checks, lint, builds; six legacy production builds; source and emitted package boundaries.
• Both packed production consumers: 11 browser scenarios each, exactly 3 history reads, 7 runs, 1 handler invocation, and 6 component submissions. Includes full interrupt payloads, paused delivery, Stop retention, next-submit clearing, history replacement, and lifecycle cleanup.
• Native observer tests: 7 per framework. Compiler-emitted installed declarations preserve readonly payload/metadata and heterogeneous tool inference.
• 414 focused infrastructure tests; 1,456 inventory records with all prior assignments and 550 legacy exports preserved.
• Independent specification and quality reviews passed, including final whole-PR review.

Verified local evidence and reproducible source fingerprint. CI results will be reported against the PR head; local verification does not claim CI success.

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Project	Deployment	Actions	Updated
threadplane	Ready	Preview	Sep 22, 2026 4:42am UTC

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