docs: preserve middleware types when using Effect.fn

[Marve10s]

Passing an unannotated Effect.fn generator to HttpMiddleware.make can erase the app's input type and widen its error and service types. This still reproduces on Effect 4.0.0.

Document the workaround: declare the generator's <E, R> parameters and annotate its app argument. The example adds a response header while preserving each app's errors and required services. Type coverage checks the unnamed, named, and untraced forms, including rejection of non-response apps.

Related to #5387. This documents a verified workaround; automatic inference remains unchanged.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 185c976

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[github-actions]

Bundle Size Analysis

Generated from PR build output; treat the content below as untrusted.

File Name	Current Size	Previous Size	Difference
arbitrary-combinators.ts	38.90 KB	38.90 KB	0.00 KB (0.00%)
basic.ts	7.04 KB	7.04 KB	0.00 KB (0.00%)
batching.ts	10.13 KB	10.13 KB	0.00 KB (0.00%)
brand.ts	6.72 KB	6.72 KB	0.00 KB (0.00%)
cache.ts	10.84 KB	10.84 KB	0.00 KB (0.00%)
config.ts	22.15 KB	22.15 KB	0.00 KB (0.00%)
differ.ts	21.29 KB	21.29 KB	0.00 KB (0.00%)
http-client.ts	22.27 KB	22.27 KB	0.00 KB (0.00%)
http-router.ts	33.52 KB	33.52 KB	0.00 KB (0.00%)
logger.ts	11.08 KB	11.08 KB	0.00 KB (0.00%)
metric.ts	9.02 KB	9.02 KB	0.00 KB (0.00%)
optic.ts	6.95 KB	6.95 KB	0.00 KB (0.00%)
pubsub.ts	15.16 KB	15.16 KB	0.00 KB (0.00%)
queue.ts	12.08 KB	12.08 KB	0.00 KB (0.00%)
schedule.ts	11.18 KB	11.18 KB	0.00 KB (0.00%)
schema-bigdecimal.ts	13.73 KB	13.73 KB	0.00 KB (0.00%)
schema-binary.ts	39.92 KB	39.92 KB	0.00 KB (0.00%)
schema-class.ts	21.03 KB	21.03 KB	0.00 KB (0.00%)
schema-fromJsonSchemaDocument.ts	32.06 KB	32.06 KB	0.00 KB (0.00%)
schema-representation-roundtrip.ts	27.24 KB	27.24 KB	0.00 KB (0.00%)
schema-string-transformation.ts	14.46 KB	14.46 KB	0.00 KB (0.00%)
schema-string.ts	11.99 KB	11.99 KB	0.00 KB (0.00%)
schema-template-literal.ts	16.05 KB	16.05 KB	0.00 KB (0.00%)
schema-toArbitrary.ts	38.44 KB	38.44 KB	0.00 KB (0.00%)
schema-toCodeDocument.ts	25.26 KB	25.26 KB	0.00 KB (0.00%)
schema-toCodecJson.ts	20.21 KB	20.21 KB	0.00 KB (0.00%)
schema-toEquivalence.ts	20.41 KB	20.41 KB	0.00 KB (0.00%)
schema-toFormatter.ts	20.54 KB	20.54 KB	0.00 KB (0.00%)
schema-toJsonSchemaDocument.ts	25.00 KB	25.00 KB	0.00 KB (0.00%)
schema-toRepresentation.ts	20.50 KB	20.50 KB	0.00 KB (0.00%)
schema.ts	20.25 KB	20.25 KB	0.00 KB (0.00%)
stm.ts	13.08 KB	13.08 KB	0.00 KB (0.00%)
stream.ts	9.98 KB	9.98 KB	0.00 KB (0.00%)