feat: interactive Ink REPL as bare zcode-acp default (ADR-0007)

[william0wang]

Summary

Every surface of the package now lives under one command — zcode-acp — with an interactive terminal chat as the bare default (ADR-0007).

Unified CLI + bin pruning

• Bins pruned to zcode-acp and zcode-acp-server, both symlinks to dist/cli.js; dispatch keys off basename(argv[1]), so existing editor configs keep working unchanged.
• Subcommands: quota (was the zcode-quota bin), hub (was zcode-acp-hub), server. Old bin files stay in dist/bin/ because bridges spawn the hub by absolute path.
• README carries the 0.11 → 0.12 migration table.

Interactive REPL (bare zcode-acp)

• Ink UI (same renderer as Claude Code / Gemini CLI) speaking ACP to a spawned bridge over stdio.
• Streaming output with code-fence coloring, dim thinking lines, live tool rows, arrow-key permission picker, Ctrl-C turn cancel (idle: press twice to quit).
• FIFO prompt queue: follow-ups submitted mid-turn run after the turn ends instead of clobbering live state.
• Bulk-paste segmentation (splitBulkInput): every CR/LF-separated line submits; nothing silently dropped.
• Sessions persist in the ZCode backend and remain available to editors.

Hardening

• Entry points (index.ts, bin/hub.ts, bin/quota.ts) export main() behind invokedDirectly guards that normalize Windows backslash paths.
• Bare invocation without a TTY falls back to the stdio server — Windows npm shims spawn node …\dist\cli.js, losing the bin name from argv; explicit zcode-acp repl still hard-fails without a TTY.
• acpx dependency dropped before release (headless-only, superseded by the in-house REPL); engines stay >=22.0.0.

Test plan

• pnpm build / pnpm typecheck / pnpm lint green
• 721 tests pass (52 files), including 3 new splitBulkInput tests and updated dispatcher tests
• Real TTY smoke (expect): session ready → prompt turn → streamed reply → /exit clean exit, zero stray processes
• No-TTY behavior: bare zcode-acp < /dev/null runs the server and exits 0 on EOF; zcode-acp repl errors with exit 2
• stdio server answers initialize with agent info through the unified entry
• Full cross-review report (5 findings, all fixed): .zcode/reviews/2026-08-25-unified-cli-review.md (local)