[justrach]

Stacked on #1804 (its commit is the first one here); merging this PR lands both.

Claude Agent: a response streaming during a tool re-list is kept (#1804)

While graff waited for Claude Code to re-read its tool list, it dropped stream events. A response already under way lost its message_start, and the turn failed with unparseable response. Lines read during that wait are now kept in order and read first by the turn. scripts/test-claude-agent.py covers it with a fake claude that streams during the re-list.

ACP: explain an exhausted empty-reply retry (#1802)

LiveTurn.errorMessage used last_api_error only for ApiError and auth failures, so EmptyCompletion reached clients as a bare error name. It now carries the explanation: the turn stopped, the conversation is kept, and sending again retries. The retry policy is unchanged. acp_live_turn.zig's tests are now compiled into the unit suite.

Simulator tests no longer overwrite the Mac's clipboard (#1801)

With the Simulator app open and Edit > Automatically Sync Pasteboard on (PasteboardAutomaticSync, the default), a simulator test that copies text replaces the host clipboard. A shell command that runs simulator tests (xcodebuild test / test-without-building, xctest) or writes a simulator pasteboard (simctl pbcopy / pbsync) is now refused in two cases: while the app is open with sync on, or when that can't be checked. The refusal asks the user to quit the app or turn sync off. graff never changes the setting and never saves or restores the clipboard. GRAFF_ALLOW_SIM_PASTEBOARD=1 turns the check off. A project's own test script is not recognized.

Large uploads are bounded by progress, not the head deadline (#1785)

Connect, upload and the response-head wait now have separate budgets (src/http_send.zig):

• Connect: the head budget.
• Upload: written in 16 KiB chunks. It fails after the head budget with no chunk accepted, or after head + 1 s per 16 KiB in total (15 min cap).
• Head: measured from the last body byte, the head budget plus 1 s per 64 KiB, clamped to the read budget.

HTTP/2 uses the size-scaled total, since http-zig reports no upload progress. Esc still cancels every stage. Loopback tests cover two cases: a paced 2 MiB upload completes past the head budget, and a peer that stops reading fails within a bound.

A loaded or forked ACP chat is a peer under its own session id (#1803)

session/load and session/fork switch the chat to another save, but its peer presence record kept the process's startup name. Mail sent to the chat's ACP session id, which is how Harness reaches a working graff chat (justrach/harness#729), found no live agent. Both now re-register their labels, as /resume and /fork in the REPL already do. scripts/test-acp-session-load.py checks graff peer list after a load; v0.302.69 fails that check.

Tests

Tier 1 green locally (3627 tests).

Closes #1785, closes #1801, closes #1802.