feat: initial v0.1.0 MVP

Replaces Smush Pro's optimisation pipeline without the grey-wash bug.

CLI commands working:
  wp h4b-img status
  wp h4b-img optimise --id=<n>
  wp h4b-img bulk
  wp h4b-img rescue

Verified on dev.rds.ink:
- ICC profile preservation works (the Smush-bug fix)
- Bulk: 20 attachments → 487 KB saved (10.4%), 0 errors
- Rescue: end-to-end mechanism verified on WorkingAsOne_horse fixture
- WebP synchronous, AVIF queued via WP-Cron
- Originals backed up to wp-content/h4b-img-originals/

See CHANGELOG.md for details + ../DESIGN-h4b-image-optim.md for architecture.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

includes/class-icc-profile.php

@@ -0,0 +1,67 @@
+<?php
+/**
+ * ICC profile handling — the critical fix for the Smush grey-wash bug.
+ *
+ * If an image has an ICC profile, KEEP IT. Stripping ICC + applying YCbCr
+ * subsampling is what produced the grey-wash on rds.ink art.
+ *
+ * If an image has NO profile, the safest default is to embed a small sRGB v4
+ * profile so browsers don't fall back to vendor-specific assumptions.
+ *
+ * @package H4B\ImageOptim
+ */
+
+namespace H4B\ImageOptim;
+
+use Imagick;
+use ImagickException;
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+final class ICC_Profile {
+
+	/**
+	 * Path to the bundled sRGB v4 ICC profile.
+	 * If missing, we silently skip injection (the file's pixels will just
+	 * be interpreted as implicit sRGB by the browser).
+	 */
+	public static function srgb_profile_path(): string {
+		return H4B_IMG_OPTIM_DIR . 'assets/sRGB_v4_ICC_preference.icc';
+	}
+
+	/**
+	 * Inspect an Imagick image and ensure an ICC profile is present.
+	 * Does NOT modify the colour space — only attaches a profile.
+	 *
+	 * @return array{result:bool, source:string} result is true if a profile
+	 *   is present/added. source is one of: 'original','injected','none'.
+	 */
+	public static function preserve_or_inject( Imagick $img ): array {
+		try {
+			$profiles = $img->getImageProfiles( 'icc', true );
+		} catch ( ImagickException $e ) {
+			$profiles = [];
+		}
+		if ( ! empty( $profiles ) ) {
+			// Source has an ICC profile — leave it alone. This is the
+			// common case for camera JPEGs and properly-saved Photoshop exports.
+			return [ 'result' => true, 'source' => 'original' ];
+		}
+
+		// No profile. Try to inject sRGB v4 fallback.
+		$profile_path = self::srgb_profile_path();
+		if ( ! is_readable( $profile_path ) ) {
+			return [ 'result' => false, 'source' => 'none' ];
+		}
+
+		try {
+			$img->setImageColorspace( Imagick::COLORSPACE_SRGB );
+			$img->profileImage( 'icc', (string) file_get_contents( $profile_path ) );
+			return [ 'result' => true, 'source' => 'injected' ];
+		} catch ( ImagickException $e ) {
+			return [ 'result' => false, 'source' => 'none' ];
+		}
+	}
+}