docs(storage): document CRAWLEE_STORAGE_DIR for local file-backed storage

[DaveHanns]

Summary

The JavaScript SDK sections of the storage pages refer to {APIFY_LOCAL_STORAGE_DIR} as the placeholder for the local storage root. That variable is no longer respected by Apify SDK v3 — it reads CRAWLEE_STORAGE_DIR (inherited from Crawlee v3). apify run sets it automatically (see src/commands/run.ts in apify-cli), so users staying on the CLI never see the mismatch. But users who launch their compiled entry point directly (tsx src/main.ts, node dist/main.js, unit tests, IDE run configurations, ...) get bitten.

Reproducer

# Fresh Actor scaffolded from a TypeScript template
apify create my-actor -t js-crawlee-cheerio-ts  # or any v3-based template
cd my-actor

# Run the compiled entry point directly, bypassing `apify run`
APIFY_IS_AT_HOME=0 APIFY_LOCAL_STORAGE_DIR=./storage tsx src/main.ts

Expected: the SDK persists the default key-value store / dataset / request queue under ./storage.

Actual:

ApifyApiError: Authentication token was not provided
    path: /v2/key-value-stores

The SDK ignores APIFY_LOCAL_STORAGE_DIR, treats storage as unconfigured, and falls back to the platform HTTP client — which then fails because no APIFY_TOKEN was provided. Setting APIFY_IS_AT_HOME=0 on its own is not enough. The fix is:

CRAWLEE_STORAGE_DIR=./storage tsx src/main.ts

Nothing in the docs points to CRAWLEE_STORAGE_DIR, so the only way to discover it today is to grep node_modules/@apify/* or node_modules/@crawlee/*.

Changes

• sources/platform/storage/key_value_store.md — JS SDK section: rename the path placeholder to {CRAWLEE_STORAGE_DIR} and add an info callout explaining the env var, the failure mode, and a working example.
• sources/platform/storage/dataset.md — JS SDK section: rename the path placeholder and cross-link to the callout.
• sources/platform/storage/request_queue.md — JS SDK section: same.

The Python SDK sections are left untouched — the Python SDK uses a different storage backend and env var, and this issue is JS-specific.

Test plan

• pnpm build (or the docs preview) renders the three pages without broken links or admonition errors.
• Follow the CRAWLEE_STORAGE_DIR=./storage tsx src/main.ts example on a fresh v3 template and confirm files land under ./storage/key_value_stores/default/.

Surfaced during an evaluation of Apify surfaces for agent-driven Actor development.

[apify-service-account]

✅ Preview for this PR (commit 1ba32ed) is ready at https://pr-2738.preview.docs.apify.com (see action run).