Research: enforce Brownian A/M/P generator semantics

[mountain]

Outcome

Correct the Brownian research method before recurrence or heat-kernel work continues.

• make native process grammars executable and generator-aware;
• require AMP profiles to declare A, M, P, all three pair relations, and the A/P closure escape;
• require native events and task claims to cover their declared generators;
• relabel merged Brownian S0/S1 as a PRE-AMP discrete control with only A-step;
• implement the positive-position chart with a typed zero/negative-domain obstruction;
• implement an exact finite exponential-observer carrier with A shift, M scale, and integer-P replica composition;
• certify the fifth replica coefficient-by-coefficient against endpoint fibres;
• retain noninteger-P closure and path-information loss as explicit residuals;
• keep recurrence, continuum, heat-kernel, Public/Experimental API, and Theory Map promotion unauthorized.

Evidence

• focused firewall/Brownian suite: 54 passed;
• full repository: 826 passed, 25 skipped, 1 pre-existing deprecation warning;
• git diff --check and Python compileall passed.

Closes #160.
Relates to #158.