release v0.1.56

[ranxianglei]

Release commit bumps BOTH fields per this repo's convention:

• billion-context-pi 0.1.55 → 0.1.56
• acp-kernel 0.0.48 → 0.0.50 (exact pin)

Why this release

Drops the ref-slot reclamation that shipped in acp-kernel 0.0.48 (PR #176, reverted in kernel #191). That code pruned and re-issued ref numbers every turn, which can silently misattribute on decompress (wrong content, not an error) — violating the id-immutability invariant now recorded in AGENTS.md (#280).

Pre-flight

• kernel 0.0.50 verified live on npm (npm view acp-kernel version) before this bump
• npm run typecheck ✓
• npm test: local sandbox has 67 known environment failures (node 25 local vs 22/24 CI, runContextRound mock hits undefined[0]); fail set is byte-identical between kernel 0.0.48 and 0.0.50 — zero behavioral delta from the upgrade; CI on master runs the same suite green (node 22/24) and is the authority
• npm run build ✓; grep -c pruneDeadRefs dist/index.js → 0 (reclamation gone from the bundle)

[github-actions]

📦 Built Extension Artifact

Branch: 2026-09-03_release-v0.1.56 (a91e71b)

Option A — Install from npm PR tag (recommended)

pi install npm:billion-context-pi@pr-282

Each push to this PR publishes a new version under the pr-282 npm tag.

Option B — Download artifact

1. Download the artifact from the Actions run
2. Extract the tarball and install:

tar xzf billion-context-pi-pr282.tgz
pi install ./package

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This comment is automatically updated on each push.