fix: eliminate startup blocking and read_file false completion

[zhuqingyv]

Closes the implementation gap tracked by #42. This is a stacked PR on #40 (codex/issue-39-ma) and must merge after its base.

Product outcome

• Renders a complete editable TUI shell before Agora/provider/MCP hydration.
• Connects ordinary MCP servers concurrently with ordered, isolated failure projection.
• Queues one startup message, preserves later input as draft, and keeps failures inside the TUI with retry/model-switch paths.
• Adds bounded 3200-character read_file pages, typed pagination errors, long-line cursors, machine-readable receipts, session-persistent coverage, task-scoped duplicate suppression, and hash-change invalidation.
• Blocks “fully read” completion unless every explicitly named file has contiguous receipt coverage.
• Keeps Context Usage independent from Memory state and generic tool compaction unchanged.

Verified gates

• npm run build: exit 0
• npm test: 408 total / 400 pass / 0 fail / 8 expected explicit-lane skips
• MA_RUN_PTY_TESTS=1: 6/6 pass, 0 skip
• Visual Playwright: 2/2 pass
• Startup PTY raw artifact committed: cold 5 p95 306.5ms first frame / 433.7ms editable; warm 30 p95 257.0ms / 384.7ms
• Remote DeepSeek real E2E: 198-line + 212-line files, complete markers proven, no duplicate page cursor
• Real packaged Agora + local whitelist model E2E: chat, named Memory intake, hot mount, stable base model object/load count

Release dependency

The exact Agora dependency/runtime lock remains at 0.2.0 until the stacked Agora PR publishes signed/notarized 0.2.1. A follow-up commit on this PR will lock the immutable registry integrity and manifest SHA before #42 closes.