docs: add security note for session management

[CryptAm]

Summary & Motivation

This PR adds an explicit security warning to the Session Management section of packages/embedded-provider-core/README.md.

Sessions contain sensitive cryptographic material, but this was not previously highlighted in the documentation. The added note helps better understand the security implications and follow best practices when implementing custom storage adapters.

How I Tested These Changes

This is a documentation-only change.
Verified that the added section renders correctly in Markdown and is placed immediately after the Session Management section.

Did you add a changeset?

No.
This PR only updates documentation and does not affect any package behavior, APIs, or interfaces.

Did you update the README files?

Yes.
The relevant README file was updated to include security guidance for session handling.

Summary by CodeRabbit

• Documentation
  • Added security guidelines for session management in the embedded provider documentation, covering secure storage practices, access controls, and session lifecycle best practices.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Added a Security Note section to the embedded provider core README documenting that sessions contain sensitive cryptographic material. The note recommends secure storage practices, access controls, avoiding session data logging, and clearing sessions on logout or security events.

Changes

Cohort / File(s)	Summary
Documentation packages/embedded-provider-core/README.md	Added Security Note section (+7 lines) outlining session security best practices including secure storage, access controls, and proper session clearing procedures

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: adding a security note to the README for session management documentation.
Description check	✅ Passed	The description fully addresses all required template sections with complete information about the changes, testing, changeset status, and README updates.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@packages/embedded-provider-core/README.md`:
- Line 246: Replace the bold inline text "**Security Note**" with a proper
Markdown heading (for example "### Security Note") so it becomes a heading-level
element consistent with the rest of the document; update the README entry that
currently contains the bold text to use the heading syntax and ensure
surrounding spacing/newlines match other headings to resolve the linting
violation.

[garlobrian52]

Branch protection policy must be fulfilled before merging.

[garlobrian52]

Let's work