2026.11.7.2: a launch description takes the fast path and streams its build; the built-in platform is one release - #900

2026.11.7.2: an editor's Run is answered on the fast path and shows its build (design 2026-11-07 §4.9, D19).

Changes

• mcpp run --print-launch takes the fast path when nothing changed: 0.01 s in place of 0.1 to 0.3 s. The full path records the launch it composes in the configuration's directory (launch/<program>.json); the fast path prints that record, with the request's program arguments, only when the launch it composes itself -- the one mcpp run executes there -- is the recorded one, field for field. Any other launch (a runner, an execution host, carried files) is described by the full path, which records it again. The description is the full path's by construction; no new list of refusals.
• mcpp run --print-launch --message-format json streams the build's events (plan, waiting, progress, artifact) before the mcpp.launch envelope, the last line; feature launch-stream. run --message-format json without --print-launch is refused.
• The built-in platform of the two ok-image targets is one release, openkal-platform 0.24.3 (D20; 2026.11.7.1 selected the series ^0.24): a project that states no platform builds the same versions at any time, with or without mcpp.lock. A lock recording another release does not decide, and the build names it. A newer platform needs no new mcpp: the project selects it, and a build that fails over the default while the index holds a newer release ends with a tip: naming it and the line to write. mcpp, its modules and generated launchers name mcpplibs.os =0.3.1. SPEC-013 1.5.
• Design records D19, D20 and the ok-image main-thread stack on Windows (openkal-image 0.5.2, platform 0.24.3).

Verification

• e2e 1024 (new): the fast description equals the full path's and resolves nothing; a changed source is compiled and described the same; a foreign record is not used and is rewritten; the stream is NDJSON ending in the envelope; launch-stream is stated.
• e2e 936, 993, 333, 963 (the control contract, test launch, named runners, target sets) pass; unit test_wire.
• e2e 1025 (new): the default is 0.24.3 and is locked; a lock recording 0.24.2 is not taken and is named; a stated series is taken as stated. Unit test PlatformDefault: the tip only for the default, only with a newer release. e2e 1020, 1021, 964 pass.
• Measured locally: a one-file project 0.09 s -> 0.01 s, the mcpp-ide project 0.30 s -> 0.01 s.

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