Send queued messages with Enter when Enter steers

[brsbl]

Human comments

What was wrong

The Enter-steers setting swapped submission callbacks without their input requirements, preventing Enter from sending queued messages from an empty composer.

What changed

• Both settings share submission callbacks and eligibility rules; the setting swaps which shortcut triggers each action.
• Enter sends queued messages when Enter steers; Cmd+Enter sends them when Enter queues.
• Draft steering, queueing, and the empty composer's Stop action retain their existing behavior.

How you verified

• Rebased onto 1988935a9 without conflicts; git range-diff confirms every layer commit retains its original patch.

• Merged layer head: 7ea59252222280bf1645bbc9c35b5b83e473798a. Rebase CI passed.

• The new base changes Docs only. Existing composer review and QA evidence remain applicable; screenshot captions retain their actual capture revisions.

• Remote CI passed on 342221e73ee590dcbe0c504c75f0a6ae56468d0a, including focused regressions for both settings.

• Chrome for Testing 153.0.8010.36 reproduced the bug before and passed queueing, steering, and empty-composer submission afterward.

• Source CLI readback confirmed queue contents after each action. Desktop viewport: 1440×900 at 2×.

• The requested cumulative Slop Cop and Slim PR passes retained this layer without changes or new findings.

Before: 963171ce1f38032e34bdd41c17a7454815504174 · After: 342221e73ee590dcbe0c504c75f0a6ae56468d0a · Desktop, 1440×900, 2×.

State	Before	After
Empty composer after Enter, Enter steers	Open	Open

Merge requested by the user after QA. Merged atomically with the stack as ebf29a865fddf6b5934d24af7c9fcae9dbc2edc0. Post-merge CI passed all 13 jobs.

BB-Thread-ID: thr_k3vhrnr4cw

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