v0.1.4

Citation ergonomics — for both code and prose. Follow-on to 0.1.3's
BM25-quality theme: retrieval is now precise, but the assembled context
returned to the LLM left the user staring at a def line without the
implementation, or at a deep section paragraph without its parent heading.
Both gaps closed by default; both have explicit opt-out knobs. Plus three
prose-side fixes that surfaced during the audit (setext headings, PDF
heading heuristic, plumbing).

Changed

• Document::context(query) on a code chunk now attaches ±1 neighbor
  chunks by default. Code is chunked as fixed-token windows so a 50-line
  function often spans 2-3 chunks; a hit on the chunk containing the def
  line would previously cite only the signature, omitting the body in the
  next chunk. With DocumentConfig::code_neighbors_default = 1
  (the new default), citations on code hits include the surrounding
  implementation. Behavior change for code-shaped corpora — set
  code_neighbors_default: 0 to restore the old chunk-only behavior. No
  effect on prose corpora (fires only on chunks tagged
  metadata["kind"] == "code").
• Document::context(query) on a prose chunk with a section heading
  now attaches the section's opener chunk by default. A query that
  lands deep inside ## Refunds → ### Eligibility previously cited only
  the matched chunk — the LLM lost the section title. With
  DocumentConfig::prose_heading_default = true (the new default), the
  section's first chunk is attached. Behavior change for hierarchical
  prose — set prose_heading_default: false to disable. Only fires on
  chunks that carry non-empty metadata["heading"] (markdown, DOCX,
  PPTX, XLSX, and — new in this release — PDF).
• Markdown sections now recognize setext headings (Title\n=====
  for H1, Title\n----- for H2) in addition to ATX (#/##/…). YAML
  frontmatter (--- ... --- at file start) is detected and excluded
  from setext scanning so its closing fence doesn't get treated as an
  H2 underline. Pandoc output / older docs / man pages now produce the
  same section structure as their ATX equivalents.
• PDF chunks now carry best-effort heading metadata. A per-page
  heuristic lifts the first short, non-paragraph-shaped line into
  Section::heading (rejecting page-number footers, body lines ending
  in sentence punctuation, and lines ending in a digit). Lets the BM25
  heading-field search added in 0.1.3 actually reach PDF chunks by
  topic; previously metadata["heading"] was always None on PDFs.

Added

• DocumentConfig::code_neighbors_default: usize (default 1).
• DocumentConfig::prose_heading_default: bool (default true).
  Both inherited via the Python / Node bindings' default config; no
  binding-surface change for callers who don't override.

Fixed

• (No code-bug fixes — 0.1.3 already closed the BM25 quality gaps. See
  the Notes section for the verified-not-broken embedding-persistence
  story.)

Notes

• Embedding persistence verified. The 0.1.3 audit suspected that
  read_folder_with(persist=true) re-embedded every chunk on reload
  (paying ~30-60 sec of bge-small cost per cold start on a 1000-chunk
  codebase). The machinery is already correct: embedded_chunks()
  populates the Chunk::embedding field from the retriever cache before
  writing index.json, Embedding is Serialize/Deserialize, and
  LocalRerankRetriever::index short-circuits any chunk that comes back
  with an embedding already set. Round-trip test
  (crates/redhop/tests/embedding_persistence.rs) now pins this — a
  reload triggers exactly 1 embed call (the query), not N+1 (the query +
  every chunk). Locked in as a regression guard.
• Eleven new tests across the citation-ergonomics theme: 3 for the code
  neighbor default, 3 for the prose heading default, 3 for setext
  headings + frontmatter handling, 2 for the PDF heading heuristic.
  111/111 tests pass under
  cargo test -p redhop --features files.