Add controlled Whisper and LLM benchmark results

Document and preserve the controlled Progeo benchmark series.

Whisper comparison:
- Compare whisper.cpp large-v3 and large-v3-turbo
- Identify and verify BUG-012: extraction stability depends on chunk size
- Repeat both transcription variants with identical reduced chunk budgets
- Select large-v3-turbo as the current production transcription model

LLM comparison:
- Compare qwen3.5:9b with qwen3.5:35B-A3B
- Preserve identical transcript, Meeting Context, prompts and chunking
- Retain qwen3.5:9b as the production recommendation
- Record runtime, repair burden and semantic-quality findings

Current production benchmark configuration:
- whisper.cpp large-v3-turbo
- target_chars=4500
- max_chars=5500
- min_chars=2500
- overlap_blocks=0
- qwen3.5:9b
- num_ctx=32768
- think=false
- temperature=0

BUG-012 remains verified but not yet fixed in the production chunker.

samples/benchmarks/progeo_whisper_turbo_20260805_120903/chunks/manifest.json

@@ -0,0 +1,86 @@
+{
+  "source_file": "progeo_whispercpp_vulkan_turbo_trimmed_converted.json",
+  "chunk_count": 10,
+  "chunks": [
+    {
+      "number": 1,
+      "filename": "chunk_01.txt",
+      "chars": 9077,
+      "blocks": 125,
+      "first_timestamp": null,
+      "last_timestamp": null
+    },
+    {
+      "number": 2,
+      "filename": "chunk_02.txt",
+      "chars": 9053,
+      "blocks": 103,
+      "first_timestamp": null,
+      "last_timestamp": null
+    },
+    {
+      "number": 3,
+      "filename": "chunk_03.txt",
+      "chars": 9053,
+      "blocks": 106,
+      "first_timestamp": null,
+      "last_timestamp": null
+    },
+    {
+      "number": 4,
+      "filename": "chunk_04.txt",
+      "chars": 9004,
+      "blocks": 126,
+      "first_timestamp": null,
+      "last_timestamp": null
+    },
+    {
+      "number": 5,
+      "filename": "chunk_05.txt",
+      "chars": 9015,
+      "blocks": 117,
+      "first_timestamp": null,
+      "last_timestamp": null
+    },
+    {
+      "number": 6,
+      "filename": "chunk_06.txt",
+      "chars": 9026,
+      "blocks": 107,
+      "first_timestamp": null,
+      "last_timestamp": null
+    },
+    {
+      "number": 7,
+      "filename": "chunk_07.txt",
+      "chars": 9008,
+      "blocks": 126,
+      "first_timestamp": null,
+      "last_timestamp": null
+    },
+    {
+      "number": 8,
+      "filename": "chunk_08.txt",
+      "chars": 9118,
+      "blocks": 145,
+      "first_timestamp": null,
+      "last_timestamp": null
+    },
+    {
+      "number": 9,
+      "filename": "chunk_09.txt",
+      "chars": 8483,
+      "blocks": 165,
+      "first_timestamp": null,
+      "last_timestamp": null
+    },
+    {
+      "number": 10,
+      "filename": "chunk_10.txt",
+      "chars": 5048,
+      "blocks": 91,
+      "first_timestamp": null,
+      "last_timestamp": null
+    }
+  ]
+}