feat(examples): add Codex memory plugin example

[0xble]

Description

Add a Codex memory plugin example powered by OpenViking via MCP.

This follows the existing agent-integration pattern already used for Claude examples and keeps the Codex integration isolated under examples/.

Related Issue

N/A

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Documentation update
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactoring (no functional changes)
• Performance improvement
• Test update

Changes Made

• Add examples/codex-memory-plugin with setup docs, package metadata, TypeScript source, and built MCP server artifact.
• Expose explicit Codex memory tools: memory_recall, memory_store, memory_forget, and memory_health.
• Reuse the same OpenViking recall-feedback pattern so recalled memory URIs are marked as used() without blocking tool responses.

Testing

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have tested this on the following platforms:
  • Linux
  • macOS
  • Windows

Verified locally with:

cd examples/codex-memory-plugin
npm ci
npm run build

Checklist

• My code follows the project's coding style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Screenshots (if applicable)

N/A

Additional Notes

• This example is additive only and does not change existing Claude or OpenClaw integrations.
• The example reads connection details from ~/.openviking/ov.conf and is intended as a copyable integration pattern for Codex users.

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[github-actions]

Failed to generate code suggestions for PR

[qin-ctx]

Thanks for the contribution. Before this is merged, could you please supplement a few reviewer-facing details so the example is easier to verify end to end?

• Runtime verification: the current PR body shows npm ci and npm run build, which confirms install/build, but not that the MCP server actually ran successfully with Codex. Please add the exact manual verification you performed end to end against a running OpenViking server.
• Functional status: please state clearly whether memory_recall, memory_store, memory_forget, and memory_health were all exercised successfully on macOS, and whether there are any known limitations or untested paths.
• Screenshots / terminal captures: since this is an integration example, a short terminal capture or screenshot showing codex mcp add, the server starting, and at least one successful tool invocation would make review much easier.
• Testing note: if no automated tests are being added for this example, please explicitly explain why, and what manual validation is being used instead.
• Flow / design diagram: the README already describes the recall feedback sequence. Please add a small flow or sequence diagram showing Codex -> MCP server -> OpenViking, especially the async used() / commit() path, so reviewers can understand the interaction model quickly.

That additional context would make the feature much easier to review and validate.