chore(cli): bump to v0.2.6 + revert unrelated __init__.py docstring

Addresses review feedback on #5152:

  - Revert the mem0/__init__.py module docstring (was a misguided
    workaround to fire ci.yml; reviewer correctly flagged as unrelated)
  - Bump cli-python and cli-node to 0.2.6 so the claim-flow tip wording
    fix ships to users in the next release
  - Add CLI v0.2.6 changelog entry under docs/changelog/sdk.mdx

The build_mem0/build_embedchain required-check stalemate on docs-only
PRs needs a proper ci.yml fix in a separate PR (passthrough job for
the path-filter-skipped case). Admin override needed for this PR.

docs/changelog/sdk.mdx

@@ -1323,6 +1323,13 @@ See the [TypeScript SDK migration guide](https://docs.mem0.ai/migration/ts-v2-to
 
 <Tab title="CLI">
 
+<Update label="2026-05-16" description="Python v0.2.6 / Node v0.2.6">
+
+**Bug Fixes:**
+- **Claim flow error message:** The `email_already_claimed` tip in `mem0 init --email` previously suggested running `mem0 link <key>` — a command that doesn't exist. Replaced with honest copy pointing the user to sign in at app.mem0.ai with their existing credentials ([#5152](https://github.com/mem0ai/mem0/pull/5152))
+
+</Update>
+
 <Update label="2026-05-14" description="Python v0.2.5 / Node v0.2.5">
 
 **New Features:**