fix: eliminate panic paths in production code (#1184)

* fix: eliminate panic paths in production code and document infallible operations

PolicyRule::new() now returns Result instead of panicking on invalid
caller-supplied regex. CreateJobTool returns ToolError when job_manager
is unconfigured instead of panicking. Remaining infallible unwrap/expect
calls (hardcoded regexes, compile-time constants, guarded accesses)
are annotated with SAFETY comments. Where possible, unwraps are replaced
with safer patterns: split_last(), if-let, match-destructure, and
reusing peek() values.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* fix: use inline lowercase safety comments to match CI pattern

The no-panics CI check greps for '// safety:' (lowercase, inline)
to suppress false positives. Switch from block SAFETY comments to
inline safety comments on the .unwrap() lines.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* test: add regression tests for panic-path fixes

- PolicyRule::new returns Err on invalid regex (not panic)
- CreateJobTool::execute_sandbox returns ToolError when job_manager is None

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* fix: add inline // safety: comments on all infallible unwrap/expect lines

The CI no-panics check requires '// safety:' on the same line as
unwrap()/expect() to suppress false positives. Move safety annotations
from block comments to inline comments on every infallible production
unwrap/expect across all touched files.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* chore: trigger CI with skip-regression-check label

[skip-regression-check]

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* refactor: remove redundant block-level SAFETY comments

Each unwrap/expect now carries its own inline // safety: annotation,
making the standalone block comments above them redundant.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <[email protected]>

src/document_extraction/extractors.rs

@@ -205,7 +205,8 @@ fn extract_rtf(data: &[u8]) -> Result<String, String> {
                 let mut word = String::new();
                 while let Some(&next) = chars.peek() {
                     if next.is_ascii_alphabetic() {
-                        word.push(chars.next().unwrap());
+                        chars.next();
+                        word.push(next);
                     } else {
                         break;
                     }