fix: decide the content mode commands, name the payload digest, and wait out the stream producer

[datlechin]

main's unit suite is red on four cases, all from #2384. This fixes three; the fourth, LogRedactionTests.noCallSitePublishesErrorText, is #2970.

Menu validation coverage. setContentModeFromMenu: and toggleContentModeFromMenu: were decided in validateMenuItem alone, so the pure resolvedEnablement left them enabled by default, which is the state that ships a lit command over a window that cannot run it. They move to an arm beside the two AI query commands, which already read the same setting, and the now unused live helper goes.

MCP audit log. The outbound tool line logged a variable called fingerprint that holds the SHA-256 prefix of the tool call's payload. In this surface a fingerprint means a pairing token's, which no log line may carry, and the guard reads the vocabulary rather than the value. It is payloadDigest now, which is what it is.

Stream abort. holdingTheStreamKeepsItAlive slept 0.6 seconds and then asserted the producer had run all 20 of its 20ms rows. On a loaded runner it had run 19. It waits for the producer instead, so it still asserts that holding the stream does not abort it, without asserting the runner's load.

Also removes a pre-existing blank line after the opening brace that SwiftLint rejects once the file is linted.

The three suites pass locally, and LogRedactionTests passes with #2970 applied on top.