fix: load crash on dsh 0.1.2-alpha.5+ (settings schema), session replay lineage, and snapshot walk hardening (.gitignore, budgets, abort)

[IMJoyJ]

Summary

Three fix areas, each with tests (278 unit + integration green on Windows; CI covers Windows/Linux × Node 22/24):

1. Settings schema: zod → Schemastery (load crash). Host settings.register (dsh 0.1.2-alpha.5 and later) invokes the namespace schema as a function; a zod instance is not callable, so the plugin fails to load with TypeError: schema is not a function. Ported to Schemastery (enums via z.union, defaults kept identical), with numeric/non-empty boundary checks moved into validateCheckpointSettings so validation strength is preserved.

2. Session replay on 0.1.2-alpha.5+. Session.events getter removed in favor of snapshotEvents(); header seedLength split into isSeeded + inheritedEventCount. replaySession now uses ctx.sessions.fork() when the host provides it (same boundary semantics as the local replaySeedOf, plus open-turn validation), otherwise falls back to generation-appropriate create() options. Fork lineage is preserved instead of silently dropped.

3. Snapshot walk hardening (.gitignore + budgets + abort). The copy provider walked the whole workspace ignoring the project's own ignore intent — an intended-huge .gitignored tree (a deck-cache folder with ~871k files) made a single snapshot take hours and stall the guarded tool call indefinitely.

   • Honors .gitignore (root + nested, deeper rules and ! re-includes win, via the ignore package) evaluated before stat, so ignored subtrees cost nothing. New respectGitignore config (default true).
   • Budget guardrails: maxSnapshotFiles (default 100k) and snapshotTimeoutMs (default 180s) skip an oversized walk with a loud warning (SNAPSHOT_BUDGET_EXCEEDED) instead of stalling — a snapshot is a safety net and must never cost more than the operation it protects. maxSnapshotBytes keeps its pruning soft-quota semantics (not a walk abort).
   • Cancellable captures: per-session AbortController fired on turn/end (cancelled/interrupted) and agent/disposed (SNAPSHOT_ABORTED) — agent.cancel can now break an in-flight walk.

Test plan

• npm test: 278 pass / 0 fail (includes 12 new provider cases: gitignore root/nested/negation/toggle, files+timeout budgets, within-budget no-op, signal abort; 2 new settings-boundary cases).
• npm run test:integration: ALL PASS ×3 consecutive runs (copy flow, git flow, v1 medium flow).
• Five-language README table + intro synced; CHANGELOG (Unreleased) and ARCHITECTURE decision records D18/D19 added.

🤖 Generated with agent assistance