encoding.py: strip frontmatter from .md at extraction time

The capture endpoint (api.py:702, 833) writes Journal/Captures/*.md
files with a markdown-bold-style header block (`**type:** voice`,
`**modality:** audio`, `**status:** unprocessed`, optional `**media:**`
and `**project:**`) followed by a `---` separator. extract_text for .md
was a bare filepath.read_text, so every capture-derived chunk in
pgvector embedded the frontmatter as raw text, polluting retrieval.

Fix adds _strip_md_frontmatter, called only for the .md branch:

- Capture-style: optional leading H1 (preserved), then consecutive
  `**key:** value` lines (and blanks), terminated by `---`. The H1 is
  retained; the key/value block + separator are removed.
- YAML-style: file's first non-empty line is `---`, terminated by `---`.
  Only triggered when no heading precedes — guards against the common
  `# Title` + `---` (horizontal rule under heading) pattern seen in
  Journal/aaronai-architecture.md and four other Journal/*.md files.

Body `**bold:**` lines (e.g. `**Visual description:**` in image
captures) and body `---` horizontal rules are never touched: the scan
aborts as soon as a non-frontmatter line appears in the leading block.

briefing_generator_v2.py's split("---", 1) heuristic was reviewed and
not reused — fragile on substring matches and on documents with
multiple `---` rules.

Verified against:
- 2026-04-26-22-44-voice.md: frontmatter stripped, body retained, H1
  retained.
- 2026-04-27-04-34-image.md: frontmatter stripped, `**Visual
  description:**` and `**Voice annotation:**` body bold-headers
  retained, trailing `---` not consumed.
- Journal/aaronai-architecture.md (5 body `---` rules): output
  byte-identical to read_text (96101 chars).
- Synthetic YAML doc: stripped correctly when no leading heading.
- Synthetic plain markdown with body `---` rules: untouched.
- Empty input + heading-only file: untouched.

Existing capture chunks in pgvector retain polluted text; the fix only
affects future extractions. Backfill decision deferred — the cleanest
path is `touch -h Journal/Captures/*.md` to bump mtime and let the
watcher re-ingest naturally on the next cycle.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/encoding.py

@@ -12,6 +12,7 @@ Replaces four separate extract reimplementations and two extract-chunk-embed pat
 import hashlib
 import json
 import logging
+import re
 from pathlib import Path
 
 from docx import Document as DocxDocument
@@ -24,6 +25,62 @@ SUPPORTED = {".docx", ".pdf", ".pptx", ".txt", ".md"}
 DEFAULT_CHUNK_SIZE = 500
 DEFAULT_CHUNK_OVERLAP = 50
 
+_BOLD_KV_RE = re.compile(r"^\*\*[\w +/-]+?:\*\*")
+
+
+def _strip_md_frontmatter(text: str) -> str:
+    """Strip a leading frontmatter block from markdown, if present.
+
+    Recognizes two formats:
+      - YAML-style: file's first non-empty line is `---`, terminated by `---`.
+        Only triggered when no heading precedes — guards against `---`
+        horizontal rules that follow an H1.
+      - Capture-style: optional H1 heading, then one or more `**key:** value`
+        lines (and blanks), terminated by `---`. The H1 is preserved; the
+        key/value block + separator are removed.
+
+    Body `---` rules and body `**bold:**` lines are never touched — the scan
+    aborts as soon as a non-frontmatter line appears in the leading block.
+    """
+    lines = text.splitlines()
+    n = len(lines)
+    i = 0
+    while i < n and not lines[i].strip():
+        i += 1
+    heading = None
+    if i < n and lines[i].startswith("# "):
+        heading = lines[i]
+        i += 1
+        while i < n and not lines[i].strip():
+            i += 1
+    if i >= n:
+        return text
+    first = lines[i].strip()
+    if heading is None and first == "---":
+        j = i + 1
+        while j < n and lines[j].strip() != "---":
+            j += 1
+        if j >= n:
+            return text
+        body_start = j + 1
+    elif _BOLD_KV_RE.match(first):
+        j = i
+        while j < n:
+            s = lines[j].strip()
+            if not s or _BOLD_KV_RE.match(s):
+                j += 1
+                continue
+            if s == "---":
+                body_start = j + 1
+                break
+            return text
+        else:
+            return text
+    else:
+        return text
+    body = "\n".join(lines[body_start:]).lstrip("\n")
+    return f"{heading}\n\n{body}" if heading else body
+
 
 def _docx_cell_paragraphs(cell):
     yield from (p for p in cell.paragraphs if p.text.strip())
@@ -89,7 +146,10 @@ def extract_text(filepath: Path) -> str:
                         parts.append(notes)
             return "\n".join(parts)
         elif suffix in {".txt", ".md"}:
-            return filepath.read_text(encoding="utf-8", errors="ignore")
+            text = filepath.read_text(encoding="utf-8", errors="ignore")
+            if suffix == ".md":
+                return _strip_md_frontmatter(text)
+            return text
     except Exception as e:
         log.warning(f"Text extraction failed for {filepath.name}: {e}")
     return ""