docs(packages): fix interface-shape drift in 5 adapter docs

[ssilvius]

Summary

After shipping the docs in PR #76 I spot-read them and found real interface drift -- type names, method signatures, field tables, and import paths that did not match the current source. These would have broken every consumer that copy-pasted the examples on npm. The prior @vault-2026 technical accuracy review covered the schema sections of `core-reference.md` but did not cover the adapter package docs, which is where these bugs sit.

What was wrong

`packages/resend/docs/outbound.md`

• `EmailProvider.sendEmail`: type names wrong. Doc said `sendEmail(params: SendEmailParams): Promise`. Actual is `sendEmail(params: EmailParams): Promise<{ id: string }>`.
• `EmailParams` field table wrong: `from` is optional, `to` is a single string (not array), `cc` / `bcc` / `headers` do not exist in the type.
• Missing: full `EmailProvider` surface (mailing lists, subscribers, campaigns, audiences) was omitted entirely.
• Method calls wrong: doc called `mailService.compose(...)` and `mailService.replyToThread(...)`. Actual methods are `InboxEmailService.composeEmail` and `replyToThread`.
• Thread metadata update: doc said `messageCount`, schema has `unreadCount`.

`packages/cloudflare/docs/blob-storage.md`

• `BlobStorage` interface signatures wrong: missing `options?` parameter on `put` and `get`; `get` return type was `string | undefined` (actual is `BlobObject | null`); and `generateKey(contentHash, extension)` was missing entirely.
• Added `BlobObject`, `BlobPutOptions`, and `BlobGetOptions` alongside so consumers see the full shape.

`packages/cloudflare/docs/inbound.md`

• `InboundAdapter.handleIncoming` return type wrong: said `Promise`, actual is `Promise<{ messageId, threadId }>`.
• "Inbound email structure" section described a 14-field parsed form as if it were the input type. The actual `InboundEmail` is 4 fields: `raw: ArrayBuffer`, `from`, `to`, `headers`. The parsed fields land on the message row AFTER the adapter parses the raw bytes. Rewrote with a clear split between input shape and parsed-form schema fields.
• Classification section: `ClassificationAdapter` should be `EmailClassifier`; `summary` field does not exist on `EmailClassification` (actual fields are `tags`, `priority`).

`packages/workers-ai/docs/classification.md`

• Interface name wrong: `ClassificationAdapter` should be `EmailClassifier`.
• Method signature wrong: `classify(message: ClassificationInput)` should be `classify(from: string, subject: string, body: string)`.
• Result type wrong: `ClassificationResult` with `summary` field should be `EmailClassification` with `tags` and `priority` fields.
• Example implementation updated to the correct shape.

`packages/cloudflare/docs/quickstart.md`

• Worker example imported `createR2BlobStorage` and `parseInboundEmail` from the package root. Actual exports are `createR2Storage` (from `/storage` subpath) and `parseEmailHeaders` / `hashContent` (from `/parsing` subpath). Also `createR2Storage` takes `{ bucket }` config, not a raw `R2Bucket`.
• `blobStorage.put(parsed.rawEmail)` was missing the required `key` parameter. Rewrote to use `storage.generateKey` + `storage.put(key, raw)`.
• `sendEmail` example showed `to: [array]`; actual is a single string.
• "Next steps" link list pointed at 5 sibling docs that only partially exist in this package. Replaced with per-package npm links.

Verification

• `pnpm test`: 609 passing across 37 files (no code change, same count as before)
• `pnpm typecheck`: clean
• `pnpm lint`: 0 warnings, 0 errors
• `oxfmt` normalized the 5 modified docs
• `legion-simplify` gate: clean

Stack

Chains off `chore/package-readmes` (#76). When #76 merges this branch rebases cleanly onto main.