proof/: add physics diagnostic/benchmark/pipelining coverage

StarForth_Physics_Diagnostic_Words.thy (physics_diagnostic_words.c):
3 of 4 words are pure-printf identity transitions; PHYSICS-BURN's guard
modelled, its arbitrary dynamically-selected func-pointer execution loop
is a new class of gap (not reducible to any prior one).

StarForth_Physics_Benchmark_Words.thy (physics_benchmark_words.c):
hot-words cache is a whole unmodelled subsystem. PHYSICS-RESET-STATS's
pipeline_metrics half (3 real vm_state fields) modelled; everything else
in the file deferred.

StarForth_Physics_Pipelining_Diagnostic_Words.thy
(physics_pipelining_diagnostic_words.c): root-cause finding --
`word_transition_metrics` has been a declared record type in
StarForth_Base.thy since early in the sweep but was never wired into
`dict_entry` as a field, so every word in this file touches state with
zero abstract representation. Three no-arg words modelled as identity
(with an explicit caveat that this reflects the model's blind spot, not
a no-op claim about the C); the three lookup words get only their
simplest empty-stack underflow case.

Suite now 43 theories, green.

proof/ROOT

@@ -25,6 +25,9 @@ session "StarForth" = "HOL-Library" +
     StarForth_Transition
     StarForth_Dictionary_Heat_Diagnostic_Words
     StarForth_Physics_Freeze_Words
+    StarForth_Physics_Diagnostic_Words
+    StarForth_Physics_Benchmark_Words
+    StarForth_Physics_Pipelining_Diagnostic_Words
     StarForth_Loop1_Heat
     StarForth_Loop2_Window
     StarForth_Loop3_Decay