fix(terminal): deliver PTY input in order

[rwanglq-ctrl]

Summary

Fast typing in the integrated terminal reached the shell out of order (#1507). VMarkPty.write() sent each keystroke as its own invoke("pty_write") without waiting for the previous one, and pty_write is an async command that writes through spawn_blocking, so concurrent writes could land in the PTY in any order.

This keeps one pty_write in flight per session and batches input that arrives meanwhile.

Policy Gates (Required)

• This PR is single-focus (one issue, one problem, one objective).
• This PR includes 100% test coverage for changed behavior and changed code paths.
• If this is a bug fix, the linked issue contains detailed reproduction context.

Linked Issue

• Fixes [Bug] Terminal: fast keyboard input reaches the shell out of order (Linux) #1507

Type of Change

• Bug fix
• Feature
• Docs
• Refactor
• Test-only
• Other

What Changed

• New src/lib/ptyInputQueue.ts: per-session ordered delivery — one write in flight, later input joined into the next batch. A failed write is reported and not retried (it may already have written a prefix). close() drops pending input without waiting for the current write.
• src/lib/pty.ts: write() goes through the queue; _cleanup() closes it, which replaces the per-write destroy guard.
• src/lib/pty.input.test.ts (5 tests): a rapid mixed-Unicode burst + Enter stays ordered with one write in flight; bracketed paste and control bytes keep their order with following input; empty writes are ignored; killing the session during a write drops queued input; a failed partial write is not replayed and later input is still accepted. The first three fail against main's pty.ts; the last two pin behaviour main already had.
• scripts/feature-map.json and .claude/feature-ledger.md: register the new module under pty-backend.

Validation

• I ran pnpm check:all locally.
• I added or updated tests to fully cover behavior changes.
• I manually verified critical flows.

Ran locally: pnpm vitest run on src/lib/pty*.test.ts, src/lib/__tests__/pty.test.ts, src/components/Terminal/spawnPty.test.ts (72 passed), pnpm typecheck, eslint on the changed files, lint:feature-map, lint:file-headers, lint:provenance-ids. Not run: the full check:all. Manual check on Linux ARM64 (Arch / Hyprland, WebKitGTK 4.1 2.52.6): bursts typed with wtype arrive at a raw-mode recorder in order, ~40 ms after the key.

UI Evidence (if applicable)

Before (from #1507): the typed string arrives scrambled, e.g. >/tmp/vmark-input-qa/received.txt became >/tm/pvmark-input-qa/receivedt.xt. After: received bytes match what was typed.

PR Checklist

• The PR avoids unrelated refactors or cleanup.
• The issue context is clear (linked issue or explanation above).
• Docs/changelog were updated if behavior or usage changed. (Bug fix only; no user-facing behavior or docs change.)
• I am ready to address review feedback.

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中文说明

问题： 在内置终端快速输入时，字符会乱序到达 shell（#1507）。前端每个按键单独调用一次 pty_write，不等上一次完成；后端 pty_write 是异步命令，并在阻塞线程池里写入 PTY，并发写入的先后顺序无法保证。

修复： 每个终端会话同一时间只保留一个在途写入请求，期间到达的输入合并成一批，按顺序发送。按键、输入法上屏和粘贴都保持顺序；写入失败不重试（可能已写入一部分）；关闭会话时丢弃未发送的输入。

验证： 新增 5 个测试，其中顺序、粘贴、空写入 3 个在 main 上失败、在本 PR 上通过，另外 2 个固定已有行为；相关终端测试 72 个全部通过。在 Linux ARM64（Arch + Hyprland）上实测，快速输入按顺序到达，约 40 ms。

🤖 Generated with Claude Code