#1970 Merge remaining trunk changes into main

Summary

• Promote all remaining trunk commits into main as trunk is being retired from active use.
• Bring checkout-first repository sandboxes and optional Relayfile attachment from #1965 into main.
• Preserve the newer main history; no branch deletion or release is requested.

Verification

• Compared main and trunk: trunk has three unique commits (the two #1965 implementation commits and its merge commit), affecting 12 files.
• Package publishing remains manually dispatched; this change does not touch Relayflows deployment trigger paths.
• Await normal mergeability and CI gates before merging.

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[!NOTE]
High Risk
Major default change for fleet spawn --sandbox affects remote worker startup and workspace context timing; new Cloud attach API and session abort behavior are on the critical fleet provisioning path.

Overview
Breaking change to Cloud sandbox defaults: fleet spawn --sandbox inside a Git repository now provisions an exact shallow checkout under /srv/agent-workforce/<repo> and dispatches without waiting for Relayfile materialization. Live workspace context before the task starts is opt-in via new --sandbox-relayfile (or --checkout --sandbox-relayfile when both Git clone and required live mirror are needed); --checkout alone no longer implies a Relayfile mount.

Adds fleet relayfile attach to mount optional Relayfile context on an already-running sandbox (Cloud sign-in, optional --path roots, shared timeout, no worker restart). The Cloud client implements attachCloudFleetSandboxRelayfile (POST relayfile-mount, 202 polling, path validation, API URL binding checks), and ensureCloudSession propagates AbortSignal so attachment deadlines cancel stalled auth refresh.

Docs, changelog (Unreleased - Major), CLI inventory counts, relayflow case 1763, and fleet tests are updated for checkout-first defaults and the new command.

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Agent Relay sessions

• claude session 47b72585 · contributor · pushed commits · last active 2026-10-13