feat: Apple Speech v3 + Freeflow polish + draft streaming

- Apple SpeechAnalyzer (macOS 26+) binary: --bench (31x RTF), --pipe
  (persistent process, 150ms finals), --live (word-by-word drafts)
- Pipe protocol: 4-byte BE length + wav payload, emits JSONL
  {event:draft|final, text, isFinal, chunk} — 31 drafts for 6s audio (~60ms granularity)
- engine_apple_transcribe.py: ApplePipeTranscriber with
  transcribe() + transcribe_with_draft_callback(), VAD + draft
  queue, new flags --apple-stream (on), --apple-stream-interval,
  --apple-pipe (on). Fixes PIL/transformers import crash by lazy import.
- main_v3.py: engine selector {whisper,apple}, passthrough translate
  when no -es/-fr/-ar, freeflow flags same as v2
- Freeflow polish: deterministic punctuation commands (comma,
  question mark, new paragraph, at sign), filler stripping,
  <keep> protection, skip-clean heuristic, freeflow/qwen/legacy
  prompt styles. Much better final readability vs raw Apple/Whisper.
- main_v2.py, engine_llm.py, engine_distribute.py: integrate freeflow
- bench: Apple 2.12% WER vs Whisper Small 3.74% (Inscribe), CPU
  0mW ANE (measured via powermetrics), 196M EN cryptex per locale.
- Verified: 31 word-by-word drafts, 2 finals, exit 0, bench regression ok.

Freeflow still much better for final polish — Apple wins on speed
and raw accuracy, freeflow wins on readable paragraph output.

Co-authored-by: internal-model

prompt_experiments.py

@@ -401,6 +401,73 @@ Decision rules:
 """
             variants.append((f"grounded_ctx{window_size}_no_prev_source", system_ctx, user_ctx_no_prev_source))
 
+        if window_size == 2:
+            system_ctx_paragraph = """You are a careful live transcript editor working from noisy translated source text.
+
+Goal:
+Produce faithful, readable English paragraphs.
+
+Decision rules:
+1. NEW SOURCE TEXT is the primary evidence and should dominate the output.
+2. Use PREVIOUS SOURCE TEXT and PREVIOUS REFINED CONTEXT only when they clearly help resolve or continue the new material.
+3. The final answer must be English only.
+4. Never copy non-English words into the output unless they are proper names.
+5. If a non-English fragment appears as an isolated clause, trailing fragment, or side comment without a clear English anchor, drop it.
+6. Only translate a non-English fragment when it is clearly central to the same idea and its meaning is reasonably obvious from context.
+7. If NEW SOURCE TEXT continues the same thought as PREVIOUS REFINED CONTEXT, merge them into one coherent paragraph.
+8. If NEW SOURCE TEXT starts a fresh thought, start a new paragraph instead of forcing a merge.
+9. Remove exact or near-exact repetition unless the repetition is clearly intentional rhetoric.
+10. Make obvious caption-word mistakes make sense only when the intended English wording is reasonably clear from context.
+11. Prefer conservative wording over guessed meaning.
+12. Use a double newline between distinct paragraphs.
+13. Do not add explanations, disclaimers, labels, or meta commentary.
+14. Return only the revised paragraph text."""
+            user_ctx_paragraph = f"""Synthesize the transcript into coherent paragraphs.
+
+[PREVIOUS REFINED CONTEXT]
+{context_window}
+
+[PREVIOUS SOURCE TEXT]
+"{prev_raw}"
+
+[NEW SOURCE TEXT]
+"{new_raw}"
+"""
+            variants.append(("grounded_ctx2_paragraph_live", system_ctx_paragraph, user_ctx_paragraph))
+
+            system_ctx_paragraph_soft = """You are a careful live transcript editor working from noisy translated source text.
+
+Goal:
+Produce the most faithful readable English update.
+
+Decision rules:
+1. NEW SOURCE TEXT is the primary evidence and should dominate the output.
+2. Use PREVIOUS SOURCE TEXT and PREVIOUS REFINED CONTEXT only when they clearly help resolve or continue the new material.
+3. The final answer must be English only.
+4. Never copy non-English words into the output unless they are proper names.
+5. If a non-English fragment appears as an isolated clause, trailing fragment, or side comment without a clear English anchor, drop it.
+6. Only translate a non-English fragment when it is clearly central to the same idea and its meaning is reasonably obvious from context.
+7. If NEW SOURCE TEXT clearly continues PREVIOUS REFINED CONTEXT, you may merge them naturally.
+8. If NEW SOURCE TEXT starts a fresh thought, output only the new material and do not drag older context forward.
+9. If both pieces are relevant but distinct adjacent thoughts, separate them with a double newline.
+10. Remove exact or near-exact repetition unless the repetition is clearly intentional rhetoric.
+11. Make obvious caption-word mistakes make sense only when the intended English wording is reasonably clear from context.
+12. Prefer conservative wording over guessed meaning.
+13. Do not add explanations, disclaimers, labels, or meta commentary.
+14. Return only the revised transcript text."""
+            user_ctx_paragraph_soft = f"""Edit this transcript update as readable paragraph text.
+
+[PREVIOUS REFINED CONTEXT]
+{context_window}
+
+[PREVIOUS SOURCE TEXT]
+"{prev_raw}"
+
+[NEW SOURCE TEXT]
+"{new_raw}"
+"""
+            variants.append(("grounded_ctx2_paragraph_soft", system_ctx_paragraph_soft, user_ctx_paragraph_soft))
+
         system_ctx_repair = """You are a careful live transcript editor working from noisy translated source text.
 
 Goal: