Fix merged lane-launch ownership, privacy, and --attach regressions

[jaeyunha]

Context\n\nPR #286 merged to dev as 3a4285c0ef0f42d98269aeb6bc61bd4fe9f11c6a while three current-head review findings remained unresolved. Parent spec #285 was then closed. These are concrete follow-up regressions and block the live Mac-mini rollout/release gate.\n\n## Defects\n\n1. P1: command submission can target an unrelated existing tmux session\n - src/tmux_wrapper.rs currently accepts DetachedSessionOutcome::PossiblyExecuted for command lanes and proceeds to identity-marker writes and send-keys.\n - Reproduction boundary: reserve the requested session name with an unrelated tmux session so tmux new-session -s <name> fails. The lane launch must stop without writing markers or submitting the command.\n - Original finding: https://github.com/Yeachan-Heo/clawhip/pull/286#discussion_r3562892911\n\n2. P2: raw Discord thread ID leaks from lane launch JSON\n - emit_lane_result inserts args.thread as thread_id for tmux new --thread ... --json.\n - Public/status output should use the same redacted or fingerprinted target representation as other lane projections.\n - Original finding: https://github.com/Yeachan-Heo/clawhip/pull/286#discussion_r3562892913\n\n3. P2: lane-aware --attach is silently ignored\n - The lane-aware early return routes through launch_lane_session, which never invokes attach_session.\n - clawhip tmux new --thread ... --attach creates/launches the lane and exits instead of attaching.\n - Original finding: https://github.com/Yeachan-Heo/clawhip/pull/286#discussion_r3562908691\n\n## Done when\n\n- Add focused regression tests for all three paths.\n- A failed/non-owned command-lane creation has no marker or command-submission effect on the pre-existing session.\n- JSON launch output does not expose the raw private thread target.\n- --attach behavior remains compatible for lane-aware launches.\n- cargo fmt --check, cargo clippy -- -D warnings, and cargo test pass.\n- Complete a live Discord/Mac-mini canary before patch release.\n\nThe installed Mac-mini canary remains on the narrower fork patch until these regressions are resolved.

[Yeachan-Heo]

Issue #287 repair is implemented and published as PR #288 against dev.

Exact head: 833620003d4128279c82af022166314e7e64c7ed

Completed locally:

• command-lane same-name collision stops at NoWorkerEffect / session-create-failed with no marker, send, cleanup, or attach effects on the unrelated session
• lane launch JSON uses the canonical fingerprinted Discord thread target and does not emit the raw thread ID
• lane-aware --attach reuses the existing helper after successful owned/finalized launch and propagates attach failure
• focused regressions and full lane integration suite pass
• cargo fmt --check, cargo check, cargo clippy -- -D warnings, cargo test, and git diff --check pass
• scoped exact-change GJC Architect review: CLEAR / APPROVE; CLI adversarial QA: passed

Current gate state: GitHub CI is in progress on the exact head. No merge or release has been performed. The live Mac-mini/PTY/Discord canary remains a post-review/merge release gate and was not performed or claimed because that environment is not explicitly available here.

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[repo owner's gaebal-gajae (clawdbot) 🦞]

[Yeachan-Heo]

Gate update for PR #288 at exact head 833620003d4128279c82af022166314e7e64c7ed:

• scoped exact-change GJC Architect review: CLEAR / APPROVE
• executor CLI adversarial QA: passed
• GitHub CI: green (Format, Check, Clippy, Test, and Build succeeded)
• PR remains open and unmerged against dev

This is a non-terminal implementation update. The live Mac-mini/PTY/Discord canary remains a post-review/merge release gate and has not been performed or claimed. No release has been performed.

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[repo owner's gaebal-gajae (clawdbot) 🦞]

[Yeachan-Heo]

Merged-dev verification passed for PR #288 at exact dev SHA a2efd1c8d1d001cd7ad7e3619a43b81db6b2d8b9.

Evidence:

• repaired reviewed head: 2a79ac9ac83d15800a605ac862258d4bb1174e6f
• exact-head hosted CI: Format, Check, Clippy, Test, and Build succeeded
• clean detached merged-dev worktree: verified
• cargo build: passed
• lane integration suite: 22/22 passed, including ownership collision, truthful ambiguity, exact retained attach, real PTY stdio inheritance, and legacy parity
• full cargo test: passed (682 unit tests plus all integration targets)
• merged-dev CLI help/dogfood: passed

The three #287 regressions and the adversarial follow-up ownership blockers are resolved. Closing only after merged-dev verification, because merge into non-default dev did not auto-close the issue.

Release remains held solely on the authorized live Mac-mini + PTY + Discord canary. This environment is Linux and no live Discord credentials/target were available or used. No release or publish action was performed.

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[repo owner's gaebal-gajae (clawdbot) 🦞]