perf: integer-only Bareiss determinant via BigInt (#64)

AGENTS.md

@@ -160,12 +160,42 @@ just examples         # Run all examples
 - Use `just changelog` to regenerate
 - Use `just changelog-unreleased <version>` to prepend unreleased changes
 
+### GitHub CLI (`gh`)
+
+When using `gh` to view issues, PRs, or other GitHub objects:
+
+- **ALWAYS** use `--json` with `| cat` to avoid pager and scope errors:
+
+  ```bash
+  gh issue view 64 --repo acgetchell/la-stack --json title,body | cat
+  ```
+
+- To extract specific fields cleanly, combine `--json` with `--jq`:
+
+  ```bash
+  gh issue view 64 --repo acgetchell/la-stack --json title,body --jq '.title + "\n" + .body' | cat
+  ```
+
+- **AVOID** plain `gh issue view N` — it may fail with `read:project`
+  scope errors or open a pager.
+
+- For **arbitrary Markdown** (backticks, quotes, special characters) in
+  comments, prefer `--body-file -` with a heredoc:
+
+  ```bash
+  gh issue comment 64 --repo acgetchell/la-stack --body-file - <<'EOF'
+  ## Heading
+
+  Body with `backticks`, **bold**, and apostrophes that's safe.
+  EOF
+  ```
+
 ### GitHub Issues
 
 Use the `gh` CLI to read, create, and edit issues:
 
-- **Read**: `gh issue view <number>` (or `--json title,body,labels,milestone` for structured data)
-- **List**: `gh issue list` (add `--label enhancement`, `--milestone v0.3.0`, etc. to filter)
+- **Read**: `gh issue view <number> --json title,body,labels,milestone | cat`
+- **List**: `gh issue list --json number,title,labels --jq '.[] | "#\(.number) \(.title)"' | cat` (add `--label enhancement`, `--milestone v0.4.0`, etc. to filter)
 - **Create**: `gh issue create --title "..." --body "..." --label enhancement --label rust`
 - **Edit**: `gh issue edit <number> --add-label "..."`, `--milestone "..."`, `--title "..."`
 - **Comment**: `gh issue comment <number> --body "..."`
@@ -205,8 +235,9 @@ When creating or updating issues:
   - `src/lu.rs`: `Lu<const D: usize>` factorization with partial pivoting (`solve_vec`, `det`)
   - `src/ldlt.rs`: `Ldlt<const D: usize>` factorization without pivoting for symmetric SPD/PSD matrices (`solve_vec`, `det`)
   - `src/exact.rs`: exact arithmetic behind `features = ["exact"]`:
-    - Determinants: `det_exact()`, `det_exact_f64()`, `det_sign_exact()` via Bareiss in
-      `BigRational`; `det_sign_exact()` adds a Shewchuk-style f64 filter for fast sign resolution
+    - Determinants: `det_exact()`, `det_exact_f64()`, `det_sign_exact()` via integer-only
+      Bareiss in `BigInt` (`bareiss_det_int`); `det_sign_exact()` adds a Shewchuk-style
+      f64 filter for fast sign resolution
     - Linear system solve: `solve_exact()`, `solve_exact_f64()` via Gaussian elimination
       with first-non-zero pivoting in `BigRational`
 - Rust tests are inline `#[cfg(test)]` modules in each `src/*.rs` file.

REFERENCES.md

@@ -28,8 +28,10 @@ matrices, see [6].
 
 ### Exact determinant sign (adaptive-precision Bareiss)
 
-`det_sign_exact()` uses a Shewchuk-style f64 error-bound filter [8] backed by exact Bareiss
-elimination [7] in `BigRational`. See `src/exact.rs` for the full architecture description.
+`det_sign_exact()` uses a Shewchuk-style f64 error-bound filter [8] backed by integer-only
+Bareiss elimination [7] in `BigInt`. Each f64 entry is decomposed into `mantissa × 2^exponent`,
+scaled to a common integer base, and eliminated without any `BigRational` or GCD overhead.
+See `src/exact.rs` for the full architecture description.
 
 ## References