v0.2.0: bounded durable ledger

Fractal Ledger v0.2.0 hardens long-horizon plan execution.

Highlights:

• structural mutations now consume their context receipt, so the next mutation requires an explicit full context refresh rendered to the agent;
• lattice_status returns a bounded actionable frontier or focused child view instead of serializing the whole durable graph;
• the store uses a revision marker and materialized cache, invalidates cross-instance state correctly, and rejects revisionless mutations;
• default snapshot cadence is 1,024 deltas.

Verification on commit 7e6885fa5ac1ce52aa58b21b6566ec1c28506560:

• pnpm test: 10 tests passed, including a real ToolRuntime proof that restores and advances a 100,000-node graph while keeping lattice_status(maxNodes: 3) under 5 KB;
• pnpm run check, publint, git diff --check, and staged TruffleHog passed;
• a fresh DeepSeek Harness web profile installed the release tarball and booted to HTTP 200.

Asset SHA-256: 60260795dbb990bd3859fc42ed720a5925793402711a0f187b7961599de97a0d.