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/cli/commands/auth_test.rs

@@ -1,22 +1,16 @@
-//! Auth test command - verify GitLab authentication.
-
 use crate::core::config::Config;
 use crate::core::error::{LoreError, Result};
 use crate::gitlab::GitLabClient;
 
-/// Result of successful auth test.
 pub struct AuthTestResult {
     pub username: String,
     pub name: String,
     pub base_url: String,
 }
 
-/// Run the auth-test command.
 pub async fn run_auth_test(config_path: Option<&str>) -> Result<AuthTestResult> {
-    // 1. Load config
     let config = Config::load(config_path)?;
 
-    // 2. Get token from environment
     let token = std::env::var(&config.gitlab.token_env_var)
         .map(|t| t.trim().to_string())
         .map_err(|_| LoreError::TokenNotSet {
@@ -29,10 +23,8 @@ pub async fn run_auth_test(config_path: Option<&str>) -> Result<AuthTestResult>
         });
     }
 
-    // 3. Create client and test auth
     let client = GitLabClient::new(&config.gitlab.base_url, &token, None);
 
-    // 4. Get current user
     let user = client.get_current_user().await?;
 
     Ok(AuthTestResult {