updated documentation

[KalanaRatnayake]

This pull request updates and clarifies the Fabric server documentation to reflect recent implementation changes, improve accuracy, and provide more precise descriptions of key components, interfaces, and behaviors. The changes cover API documentation, parser and validation plugin design, plan status handling, and struct definitions.

API and Behavior Documentation Updates:

• docs/api.md: Expanded the description of the Fabric node and updated service documentation to clarify request/response fields and behaviors for /fabric/set_plan, /fabric/set_completion, and /fabric/get_plan_status. Added /fabric/get_plan_status to the service table and improved descriptions of plan submission and status querying.
• docs/status.md: Improved the explanation of the plan status lifecycle, clarified the meaning and handling of the CANCELLED state, and detailed the request/response structure for /fabric/get_plan_status. Updated how rejected items are reported and how status codes are mapped. [1] [2] [3]

Parser and Validation Plugin Documentation:

• docs/parser_plugins.md: Refined the motivation for parser plugins, updated the interface to match the current implementation (including new methods like load_file and check_compatibility), and clarified how control flow and parallelism are handled in the default XMLParserPlugin. Adjusted the description of how runner parameters are extracted and converted. [1] [2] [3] [4] [5]
• docs/validation_plugins.md: Updated the explanation of runtime plugin selection, clarified the validation logic to match current behavior (e.g., immediate exception on unmatched interface/provider), and described how validation failures are handled by the server. [1] [2] [3]

Structs and Client Documentation:

• docs/structs.md: Updated struct field definitions to match the latest code (e.g., new event enum, instance_id, plan_id, status fields), clarified parameter and method descriptions, and fixed file path references. [1] [2] [3] [4] [5]
• docs/capability_client.md, docs/bond_client.md: Clarified initialization, parameter usage, and runtime behavior for the CapabilityClient and BondClient classes, including service waiting and bond management details. [1] [2] [3]

Testing and TODOs:

• TODO.md: Added a note to implement integration tests for /fabric/cancel_plan and /fabric/get_plan_status.

These changes ensure the documentation is consistent with the current Fabric implementation and provide clearer guidance for developers and users.