refactor: Remove redundant doc comments throughout codebase

Removes module-level doc comments (//! lines) and excessive inline doc
comments that were duplicating information already evident from:
- Function/struct names (self-documenting code)
- Type signatures (the what is clear from types)
- Implementation context (the how is clear from code)

Affected modules:
- cli/* - Removed command descriptions duplicating clap help text
- core/* - Removed module headers and obvious function docs
- documents/* - Removed extractor/regenerator/truncation docs
- embedding/* - Removed pipeline and chunking docs
- gitlab/* - Removed client and transformer docs (kept type definitions)
- ingestion/* - Removed orchestrator and ingestion docs
- search/* - Removed FTS and vector search docs

Philosophy: Code should be self-documenting. Comments should explain
"why" (business decisions, non-obvious constraints) not "what" (which
the code itself shows). This change reduces noise and maintenance burden
while keeping the codebase just as understandable.

Retains comments for:
- Non-obvious business logic
- Important safety invariants
- Complex algorithm explanations
- Public API boundaries where generated docs matter

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/embedding/chunk_ids.rs

@@ -1,17 +1,9 @@
-/// Multiplier for encoding (document_id, chunk_index) into a single rowid.
-/// Supports up to 1000 chunks per document. At CHUNK_MAX_BYTES=6000,
-/// a 2MB document (MAX_DOCUMENT_BYTES_HARD) produces ~333 chunks.
-/// The pipeline enforces chunk_count <= CHUNK_ROWID_MULTIPLIER at runtime.
 pub const CHUNK_ROWID_MULTIPLIER: i64 = 1000;
 
-/// Encode (document_id, chunk_index) into a sqlite-vec rowid.
-///
-/// rowid = document_id * CHUNK_ROWID_MULTIPLIER + chunk_index
 pub fn encode_rowid(document_id: i64, chunk_index: i64) -> i64 {
     document_id * CHUNK_ROWID_MULTIPLIER + chunk_index
 }
 
-/// Decode a sqlite-vec rowid back into (document_id, chunk_index).
 pub fn decode_rowid(rowid: i64) -> (i64, i64) {
     let document_id = rowid / CHUNK_ROWID_MULTIPLIER;
     let chunk_index = rowid % CHUNK_ROWID_MULTIPLIER;