Remove dead bilinear_resize and lattice_source_rgba

REC-117: both functions had definitions but no imports, calls, tests,
or doc references anywhere in the repo.

Kill attempts that failed: none.
- `rg -n -w 'bilinear_resize|lattice_source_rgba' src tests tools
  scripts README.md docs` -> only the two now-removed definitions
  (repeated the census command against current HEAD).
- Cross-repo `rg -n -w 'bilinear_resize|lattice_source_rgba'` over all
  of F:/Projects -> only this repo's own source and the census docs.
- Confirmed `build_source_lattice_reference`, which
  `lattice_source_rgba` called, is still used by two other live
  callers in metrics.py (lines 280, 311) and was left untouched.

Checks run: `python -m py_compile src/repixelizer/io.py
src/repixelizer/metrics.py` -> compiles cleanly. Did not run the
pytest suite: this repo's runtime dependencies include torch>=2.6.0,
which is not installed in this worktree and installing it would be a
multi-GB download outside this pass's focused-check budget; no test
file references either function by name
(`rg -n -w 'bilinear_resize|lattice_source_rgba' tests` -> no
matches), so this is a compile-level check only, stated plainly rather
than reported as a full green test run.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/repixelizer/io.py

@@ -41,12 +41,6 @@ def box_resize(rgba: np.ndarray, width: int, height: int) -> np.ndarray:
     return np.asarray(resized, dtype=np.float32) / 255.0
 
 
-def bilinear_resize(rgba: np.ndarray, width: int, height: int) -> np.ndarray:
-    image = Image.fromarray(np.clip(np.rint(rgba * 255.0), 0, 255).astype(np.uint8), mode="RGBA")
-    resized = image.resize((width, height), resample=Image.Resampling.BILINEAR)
-    return np.asarray(resized, dtype=np.float32) / 255.0
-
-
 def lanczos_resize(rgba: np.ndarray, width: int, height: int) -> np.ndarray:
     image = Image.fromarray(np.clip(np.rint(rgba * 255.0), 0, 255).astype(np.uint8), mode="RGBA")
     resized = image.resize((width, height), resample=Image.Resampling.LANCZOS)

src/repixelizer/metrics.py

@@ -496,19 +496,3 @@ def _motif_blocks(premul: np.ndarray) -> np.ndarray:
     centered = blocks - np.mean(blocks, axis=-2, keepdims=True)
     scale = np.maximum(1e-4, np.mean(np.abs(centered), axis=(-2, -1), keepdims=True))
     return centered / scale
-
-
-def lattice_source_rgba(
-    source_rgba: np.ndarray,
-    *,
-    target_width: int,
-    target_height: int,
-    alpha_threshold: float = 0.05,
-) -> tuple[np.ndarray, float]:
-    reference = build_source_lattice_reference(
-        source_rgba,
-        target_width=target_width,
-        target_height=target_height,
-        alpha_threshold=alpha_threshold,
-    )
-    return reference.mean_rgba, reference.dispersion