Add per-hex metadata system for scale-invariant classification

Each hex now gets a meta/<q>_<r>.json with stable ID, pixel center
coordinates, pixel bounds, labels, notes, and classification status.
The pixelCenter acts as a scale-independent anchor: when switching from
10 Meilen/Hex to 5 Meilen/Hex, pixelToAxial(meta.pixelCenter, newSize)
maps coarse hexes to fine hexes without re-running classification.

Adds:
- pipeline/build-hexmeta.ts: creates/updates metadata + exports
  data/hexmeta-<map-id>.jsonl (committed, survives git clones)
- pipeline/auto-classify-ocean.ts: pixel-based ocean auto-detection
- pipeline/create-map.ts: one-off DB map entry creation
- extract-submaps.ts: writes meta/<q>_<r>.json during extraction
- data/hexmeta-1.jsonl: 8844 hex metadata entries for Aventurien map 1

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pipeline/extract-submaps.ts

@@ -23,6 +23,7 @@ import { initDb, getDb } from '../server/db.js';
 import { axialToPixel, hexVertices } from '../core/coords.js';
 import { gridBoundsForImage } from '../core/hex-grid.js';
 import { HexEdge, EDGE_DIRECTIONS, ALL_EDGES, type AxialCoord, type PixelCoord } from '../core/types.js';
+import type { HexMeta } from './build-hexmeta.js';
 
 const ROOT = resolve(dirname(fileURLToPath(import.meta.url)), '..');
 
@@ -183,7 +184,7 @@ async function main() {
   const outDir = join(ROOT, 'pipeline', 'submaps', String(mapId));
   mkdirSync(outDir, { recursive: true });
 
-  // Write manifest
+  // Write manifest (with stable IDs, starting at 1)
   const manifest = {
     mapId,
     imageWidth: image_width,
@@ -192,17 +193,47 @@ async function main() {
     originX: origin_x,
     originY: origin_y,
     meilenPerHex: hexesPerMeile,
-    hexes: sorted.map(c => ({ q: c.q, r: c.r })),
+    hexes: sorted.map((c, i) => ({ id: i + 1, q: c.q, r: c.r })),
   };
   writeFileSync(join(outDir, 'manifest.json'), JSON.stringify(manifest, null, 2));
   console.log(`Manifest written: ${sorted.length} hexes`);
 
+  // Create meta directory for per-hex attribute files
+  const metaDir = join(outDir, 'meta');
+  mkdirSync(metaDir, { recursive: true });
+
   let done = 0;
-  for (const coord of sorted) {
+  for (let i = 0; i < sorted.length; i++) {
+    const coord = sorted[i];
     const filename = `${coord.q}_${coord.r}.png`;
     const outPath  = join(outDir, filename);
+    const metaPath = join(metaDir, `${coord.q}_${coord.r}.json`);
 
-    // Skip if already extracted (resumable)
+    // Create meta file if not present (never overwrite existing — preserves labels/notes)
+    if (!existsSync(metaPath)) {
+      const px = axialToPixel(coord, hex_size, origin);
+      const r  = Math.ceil(hex_size * CROP_RADIUS_FACTOR);
+      const meta: HexMeta = {
+        id: i + 1,
+        q: coord.q, r: coord.r,
+        mapId,
+        hexSizePx: hex_size,
+        meilenPerHex: hexesPerMeile,
+        pixelCenter: { x: Math.round(px.x), y: Math.round(px.y) },
+        pixelBounds: {
+          left:   Math.max(0, Math.round(px.x - r)),
+          top:    Math.max(0, Math.round(px.y - r)),
+          right:  Math.min(image_width,  Math.round(px.x + r)),
+          bottom: Math.min(image_height, Math.round(px.y + r)),
+        },
+        labels: [],
+        notes: '',
+        classification: null,
+      };
+      writeFileSync(metaPath, JSON.stringify(meta, null, 2));
+    }
+
+    // Skip PNG if already extracted (resumable)
     if (existsSync(outPath)) {
       done++;
       continue;