fix(geotiff): revert ConcurrencyLimiter to a chunkd SourceMiddleware

[kylebarron]

Written by Claude on behalf of @kylebarron

Closes #565.

Summary

chunkd #1697 shipped (@chunkd/source@11.4.1, @chunkd/middleware@11.3.1), so SourceView now forwards the request signal to middleware (and SourceChunk forwards it on multi-chunk sub-requests). That removes the reason for the LimitedSource source-wrapper workaround introduced in #557: a middleware can now observe an abort, so a request whose caller aborts while queued for a slot is dropped before any network I/O.

This reverts the limiter to the originally-intended LimiterMiddleware (a chunkd SourceMiddleware):

• limiter.ts — LimitedSource → LimiterMiddleware.
• geotiff.ts — compose the limiter into the header SourceView after SourceChunk/SourceCache (cache hits short-circuit and never burn a slot), plus a tiny SourceView wrapping the data source. getPriority threading preserved.
• deps — bump @chunkd/source / @chunkd/source-http to ^11.4.1 and @chunkd/middleware to ^11.3.1 (the middleware approach hard-requires the fix, so the floors move, not just the lockfile).
• spec — drop the temporary "implementation note" in dev-docs/specs/2026-05-19-concurrency-limiter-design.md.

Internal-only: the public API (GeoTIFF.fromUrl options, ConcurrencyLimiter, Priority, PerOriginSemaphore) is unchanged either way.

Not a blind revert

Two changes landed on main after the original workaround, so a wholesale git revert would have dropped them. Both are preserved:

• the normalizePriority (NaN) helper in limiter.ts, and
• the integration test that aborts a queued header read through the real fromUrl → SourceView → limiter path.

That integration test is the acceptance test for this change — it is unchanged and still passes, which is the end-to-end proof that the signal now reaches the middleware.

Verification

• pnpm --filter @developmentseed/geotiff test — 140 passed (16 files)
• pnpm --filter @developmentseed/geotiff typecheck — clean
• pnpm check (biome) — clean

🤖 Generated with Claude Code

[kylebarron]

LGTM!