feat(observer): node-dormancy extractor + initial JSON snapshot

Two-signal availability check: dormant=true OR boundaries contains DEFERRED.
Treats #17 (Tooling-marked) and #44/#50/#54/#67 (DEFERRED in boundaries)
uniformly as unavailable. Tooling Прил.Н unmodified — semantics preserved.

7 vitest cases (basic, multi-row, DEFERRED-fallback, boundary check).
Initial JSON: 67 nodes, 6 unavailable.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tools/.node-dormancy.json

@@ -0,0 +1,69 @@
+{
+  "#1": true,
+  "#2": false,
+  "#3": false,
+  "#4": false,
+  "#5": false,
+  "#6": false,
+  "#7": false,
+  "#8": false,
+  "#9": false,
+  "#10": false,
+  "#11": false,
+  "#12": false,
+  "#13": false,
+  "#14": false,
+  "#15": false,
+  "#16": false,
+  "#17": true,
+  "#18": false,
+  "#19": false,
+  "#20": false,
+  "#21": false,
+  "#22": false,
+  "#23": false,
+  "#24": false,
+  "#30": false,
+  "#31": false,
+  "#32": false,
+  "#33": false,
+  "#34": false,
+  "#35": false,
+  "#36": false,
+  "#37": false,
+  "#38": false,
+  "#39": false,
+  "#40": false,
+  "#41": false,
+  "#42": false,
+  "#43": false,
+  "#44": true,
+  "#45": false,
+  "#46": false,
+  "#47": false,
+  "#48": false,
+  "#49": false,
+  "#50": true,
+  "#51": false,
+  "#52": false,
+  "#53": false,
+  "#54": true,
+  "#55": false,
+  "#56": false,
+  "#57": false,
+  "#58": false,
+  "#59": false,
+  "#60": false,
+  "#61": false,
+  "#62": false,
+  "#63": false,
+  "#64": false,
+  "#65": false,
+  "#66": false,
+  "#67": true,
+  "#25": false,
+  "#26": false,
+  "#27": false,
+  "#28": false,
+  "#29": false
+}