fix(ai,tasks): Enhance AI provider robustness and task processing

This commit introduces several improvements to AI interactions and
task management functionalities:

- AI Provider Enhancements (for Telemetry & Robustness):
    - :
        - Added a check in  to ensure
          is a string, throwing an error if not. This prevents downstream
           errors (e.g., in ).
    - , , :
        - Standardized return structures for their respective
          and  functions to consistently include /
          and  fields. This aligns them with other providers (like
          Anthropic, Google, Perplexity) for consistent telemetry data
          collection, as part of implementing subtask 77.14 and similar work.

- Task Expansion ():
    - Updated  to be more explicit
      about using an empty array  for empty  to
      better guide AI output.
    - Implemented a pre-emptive cleanup step in
      to replace malformed  with
      before JSON parsing. This improves resilience to AI output quirks,
      particularly observed with Perplexity.

- Adjusts issue in commands.js where successfulRemovals would be undefined. It's properly invoked from the result variable now.

- Updates supported models for Gemini
These changes address issues observed during E2E tests, enhance the
reliability of AI-driven task analysis and expansion, and promote
consistent telemetry data across multiple AI providers.

scripts/modules/commands.js

@@ -2060,7 +2060,7 @@ function registerCommands(programInstance) {
 					);
 
 					// Exit with error if any removals failed
-					if (successfulRemovals.length === 0) {
+					if (result.removedTasks.length === 0) {
 						process.exit(1);
 					}
 				}