Collect stopped TypeScript inputs through observers

[CaelmBleidd]

TypeScript analysis discards unfinished inputs when an unknown-call fallback prunes a path or an execution limit leaves states queued. Add an opt-in TsStoppedStatesObserver that sends these inputs to a caller-provided consumer, separately from completed witnesses.

UMachine.run retains its Unit contract. The shared machine observer and machine options retain their existing APIs, and analysis results do not gain a suspended-state list. TsMachine accepts an observer factory bound to the current selector. Unknown-call prefixes are snapshotted before pruning; reachable runtime-bound states are observed before ordinary witness filtering. After successful analysis, the caller collects the remaining queue while the machine is still open. This preserves stop metadata and avoids treating an exceptional onMachineStopped callback as successful analysis. Queue collection performs no additional execution steps or SAT checks; sink failures remain visible when collection completes.

Guarded residuals keep only cached models satisfying their guard, and the step limit stops at the requested count. Void-returning calls use undefined-compatible storage, with a source-level regression test.

Validation after rebasing onto main at e09199a5a0bb9aeb6eb4eecdcbaf25a3ec16737b: 17 focused TS tests and 21 solver/selector observation tests passed, with no failures or skips. Eight Calls tests also passed with the prepared local consumer migration; that migration remains separate from this PR. Disabling queue extraction made both timeout/step-limit regression checks fail; restoring it made them pass. Whitespace checks passed. These checks establish lifecycle, prefix/model, and fixture integration behavior, not representative real-program coverage.