docs: switch local Build Cache guides to push-enabled default

[Badlazzor]

🤖 Agent-authored docs-impact review. Generated from a code change in bitrise-io/bitrise-build-cache-cli by the docs-impact-review skill. Needs human verification before merge — this is the publish gate.

Source change: bitrise-io/bitrise-build-cache-cli#528 (ACI-5380)

Changes for this code change

The CLI flipped --cache-push default from false to true for local activate on Gradle, Bazel, React Native (already merged separately as PR #466), and the interactive wizard. Local activation now behaves the same as the CI activation: read + write.

Four "in local builds" guides updated:

• bitrise-build-cache/build-cache-for-gradle/configuring-the-build-cache-for-gradle-in-local-builds.mdx — wizard step 5 now says "keep the default Yes, push too"; the ## Local builds only read from the cache and ## Pushing to the cache from local builds sections merge into ## Cache push mode (default = push) + ## Opting into pull-only mode (opt-in).
• bitrise-build-cache/build-cache-for-bazel/configuring-the-build-cache-for-bazel-in-local-builds.mdx — same wizard + section flip. Also updated the sample .bazelrc block to show --remote_upload_local_results (the new default), the "committing the configuration" subsection now frames pull-only as a deliberate developer-side override rather than "what the CLI writes", and the --noremote_upload_local_results row in the "What is safe to commit" table now reads "Optional, if you want to force pull-only".
• bitrise-build-cache/build-cache-for-react-native/configuring-the-build-cache-for-react-native-in-local-builds.mdx — same wizard + section flip.
• bitrise-build-cache/build-cache-for-xcode/configuring-the-build-cache-for-xcode-in-local-builds.mdx — same wizard + section flip. (Xcode's CLI default was already true, so the wizard-prompt copy was the only user-visible drift.)

What a reviewer must verify before merge

• The new default reads as intended — this PR frames pull-only as a deliberate opt-in for teams whose CI populates the cache; that's how the ticket motivates the flip (default trial should look non-broken).
• The wizard step-5 copy in each guide matches the CLI's new prompt description ("Default on — the build reads from and writes to the shared cache.").
• Slugs / sidebar order / partials render correctly (npm start).
• The renamed anchors (#cache-push-mode, #opting-into-pull-only-mode) don't have inbound links from other pages — I grep'd the docs repo and found none, but a partial or an auto-generated index could still reference the old anchors.
• API reference pages: correctly left untouched — no OpenAPI/spec shape changed by this diff.

Pre-existing drift NOT fixed here

Flagging these for a separate cleanup rather than expanding this PR's scope:

• The RN and Xcode local-builds pages have a :::note telling users to manually stop the xcelerate proxy / ccache helper after re-running activate with a different push setting. The CLI already auto-restarts the daemon on push flag change (see bitrise-io/bitrise-build-cache-cli PRs #477, previously). That note is stale as of that fix. Not touched here to keep this diff scoped to ACI-5380.

[github-actions]

Preview: https://docs-impact-aci-5380-local-c.bitrise-docs.pages.dev