chore: remove dead code (#648) (#703)

* chore: remove dead code (LlmEvaluator, chunk_by_paragraphs, bundled channel installer, Reasoning::safety)

Delete unused code flagged in #648:
- evaluation/success.rs: delete LlmEvaluator struct/impl, remove #[allow(dead_code)] from RuleBasedEvaluator methods
- workspace/chunker.rs: delete chunk_by_paragraphs() and its tests (zero production callers)
- extensions/manager.rs: delete install_bundled_channel_from_artifacts() (hot-activation never shipped)
- llm/reasoning.rs: remove unused safety field from Reasoning struct; cascade removal through ContextCompactor, HeartbeatRunner, LlmSoftwareBuilder, and all callers

Closes #648

[skip-regression-check]

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: move RuleBasedEvaluator into test module to fix dead_code warning

RuleBasedEvaluator has no production callers -- it was only used in
tests of itself. Moving it into #[cfg(test)] eliminates the clippy
dead_code error that broke CI.

[skip-regression-check]

Co-Authored-By: Claude Opus 4.6 <[email protected]>

---------

Co-authored-by: Claude Opus 4.6 <[email protected]>

src/extensions/manager.rs

@@ -1405,38 +1405,6 @@ impl ExtensionManager {
         Ok(())
     }
 
-    #[allow(dead_code)] // Used by upcoming hot-activation flow
-    async fn install_bundled_channel_from_artifacts(
-        &self,
-        name: &str,
-    ) -> Result<InstallResult, ExtensionError> {
-        // Check if already installed
-        let channel_wasm = self.wasm_channels_dir.join(format!("{}.wasm", name));
-        if channel_wasm.exists() {
-            return Err(ExtensionError::AlreadyInstalled(name.to_string()));
-        }
-
-        crate::channels::wasm::install_bundled_channel(name, &self.wasm_channels_dir, false)
-            .await
-            .map_err(ExtensionError::InstallFailed)?;
-
-        tracing::info!(
-            "Installed bundled channel '{}' to {}",
-            name,
-            self.wasm_channels_dir.display()
-        );
-
-        Ok(InstallResult {
-            name: name.to_string(),
-            kind: ExtensionKind::WasmChannel,
-            message: format!(
-                "Channel '{}' installed. \
-                 Run tool_auth('{}') to configure authentication, then activate.",
-                name, name,
-            ),
-        })
-    }
-
     /// Install a WASM extension from local build artifacts (WasmBuildable source).
     ///
     /// Resolves the build directory (relative to `CARGO_MANIFEST_DIR` or absolute),