User story: Register a content-source plugin

**As a** plugin developer, **I want** to register my plugin by placing a directory with a manifest and executable into the plugins folder, **so that** users can install plugins without compiling or configuring.

User story: Register a content-source plugin

As a plugin developer,
I want to register my plugin by placing a directory with a manifest and executable into the plugins folder,
so that users can install plugins without compiling or configuring.

Priority

Must

Acceptance criteria

1. Given I create a directory my-plugin/ containing a valid plugin.toml and executable, when I place it in ~/.rymflux/plugins/ and start the app, then the plugin is registered and its capabilities are available.
2. Given my plugin.toml is missing a required field (e.g., id), when the app starts, then my plugin is skipped and a log message explains what’s missing.
3. Given my plugin executable does not exist at the declared entry path, when the app tries to use the plugin, then an error is returned explaining that the entry point was not found.
4. Given I update my plugin binary, when the app next launches the plugin process, then the updated binary is used (no stale cache).

Notes / constraints

• Discovery is filesystem-scan based (FR-PLUGIN-1).
• Plugin directory scanning happens at startup only in v1 (hot-reload is v2).

Traceability

• Requirement IDs: FR-PLUGIN-1, FR-PLUGIN-2
• Feature docs: docs/user/getting-started/plugin-installation.md