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/ingestion/discussion_queue.rs

@@ -4,7 +4,6 @@ use crate::core::backoff::compute_next_attempt_at;
 use crate::core::error::Result;
 use crate::core::time::now_ms;
 
-/// Noteable type for discussion queue.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum NoteableType {
     Issue,
@@ -28,7 +27,6 @@ impl NoteableType {
     }
 }
 
-/// A pending discussion fetch entry.
 pub struct PendingFetch {
     pub project_id: i64,
     pub noteable_type: NoteableType,
@@ -36,7 +34,6 @@ pub struct PendingFetch {
     pub attempt_count: i32,
 }
 
-/// Queue a discussion fetch. ON CONFLICT resets backoff (consistent with dirty_sources).
 pub fn queue_discussion_fetch(
     conn: &Connection,
     project_id: i64,
@@ -57,7 +54,6 @@ pub fn queue_discussion_fetch(
     Ok(())
 }
 
-/// Get next batch of pending fetches (WHERE next_attempt_at IS NULL OR <= now).
 pub fn get_pending_fetches(conn: &Connection, limit: usize) -> Result<Vec<PendingFetch>> {
     let now = now_ms();
     let mut stmt = conn.prepare(
@@ -96,7 +92,6 @@ pub fn get_pending_fetches(conn: &Connection, limit: usize) -> Result<Vec<Pendin
     Ok(results)
 }
 
-/// Mark fetch complete (remove from queue).
 pub fn complete_fetch(
     conn: &Connection,
     project_id: i64,
@@ -111,7 +106,6 @@ pub fn complete_fetch(
     Ok(())
 }
 
-/// Record fetch error with backoff.
 pub fn record_fetch_error(
     conn: &Connection,
     project_id: i64,
@@ -213,7 +207,6 @@ mod tests {
             .unwrap();
         assert_eq!(attempt, 1);
 
-        // Re-queue should reset
         queue_discussion_fetch(&conn, 1, NoteableType::Issue, 42).unwrap();
         let attempt: i32 = conn
             .query_row(