fix(tool-server): key Fabric component-tree measurement by nativeTag so tap coords don't collapse to 0.5,0.5

[latekvo]

Problem

debugger-component-tree returned every element with the same tap coordinate — (tap: 0.50,0.50) — on the New Architecture (Fabric/bridgeless), making the tool's primary output (per-element tap coordinates) unusable. Reproduced live on an RN 0.81.5 Fabric app; the tree walk, skip stats, and screen size were all correct, only the coordinates collapsed.

Root cause

The injected script (utils/debugger/scripts/component-tree.ts) batch-measures host views and caches each rect under a per-host key built as (hi.f ? 'f' : 'p') + hi.n. On Fabric, getHostInfo returns the shadow node object as hi.n ({ f: true, n: fiber.stateNode.node }), so the key stringifies to "f[object Object]" for every host. All hosts collapsed to a single cache entry → only the first (root) view was measured → every component inherited the root's full-screen rect → (x + w/2)/screenW, (y + h/2)/screenH = 0.5, 0.5 for all. Paper/old-arch was unaffected because there hi.n is already a numeric nativeTag.

Fix

Key the cache by a primitive nativeTag on Fabric (fiber.stateNode.canonical.nativeTag, the same field the Paper branch already uses), with a WeakMap-by-identity fallback so distinct shadow nodes can never share a key even if nativeTag were ever absent. getHostInfo now carries an explicit key, and the three cache-key derivations use it. Paper/old-arch behavior is unchanged.

Testing

Live (first-hand), on a running RN 0.81 Fabric app — walking the live fiber tree:

	Fabric host nodes	distinct measure keys
old key ('f' + node)	2140	1 ("f[object Object]")
new key ('f' + nativeTag)	2140	2140

Unit — adds test/debugger/component-tree-script.test.ts, which evaluates the injected script against a mocked Fabric tree of three siblings at distinct positions (the existing component-tree.test.ts only covered the pure post-processor with pre-filled rects, which is why this shipped). vitest run → passes with the fix; reverting component-tree.ts to main fails it with { y: 100 } to match { y: 300 } (the second component inheriting the first's rect — exactly the collapse).