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/change_detector.rs

@@ -1,11 +1,8 @@
-//! Detect documents needing (re-)embedding based on content hash changes.
-
 use rusqlite::Connection;
 
 use crate::core::error::Result;
 use crate::embedding::chunking::{CHUNK_MAX_BYTES, EXPECTED_DIMS};
 
-/// A document that needs embedding or re-embedding.
 #[derive(Debug)]
 pub struct PendingDocument {
     pub document_id: i64,
@@ -13,20 +10,12 @@ pub struct PendingDocument {
     pub content_hash: String,
 }
 
-/// Find documents that need embedding: new (no metadata), changed (hash mismatch),
-/// or config-drifted (chunk_max_bytes/model/dims mismatch).
-///
-/// Uses keyset pagination (WHERE d.id > last_id) and returns up to `page_size` results.
 pub fn find_pending_documents(
     conn: &Connection,
     page_size: usize,
     last_id: i64,
     model_name: &str,
 ) -> Result<Vec<PendingDocument>> {
-    // Documents that either:
-    // 1. Have no embedding_metadata at all (new)
-    // 2. Have metadata where document_hash != content_hash (changed)
-    // 3. Config drift: chunk_max_bytes, model, or dims mismatch (or pre-migration NULL)
     let sql = r#"
         SELECT d.id, d.content_text, d.content_hash
         FROM documents d
@@ -79,7 +68,6 @@ pub fn find_pending_documents(
     Ok(rows)
 }
 
-/// Count total documents that need embedding.
 pub fn count_pending_documents(conn: &Connection, model_name: &str) -> Result<i64> {
     let count: i64 = conn.query_row(
         r#"