feat: support multi-slash model IDs and provider hint extraction

[hunghoang3011]

Summary

• Fix model resolution for multi-slash model IDs (e.g., aws/anthropic/bedrock-claude-opus-4-6) where the first /-segment is not a real provider, causing agents to
  fall through to free/default models
• Forward user-configured model overrides to sub-agents dispatched via call-omo-agent, which previously sent prompts without any model field

Changes

• New extractProviderHint utility (src/shared/extract-provider-hint.ts): Validates the first segment of a model string against the connected-providers cache
  before using it as a provider filter. Returns undefined for unrecognized providers, enabling cross-provider matching.
• fuzzyMatchModel cross-provider fallback (src/shared/model-availability.ts): When provider-filtered candidates = 0, retries without the provider filter instead
  of returning null immediately. Acts as a universal safety net for multi-slash IDs.
• extractModelPrefix fix (src/hooks/think-mode/switcher.ts): Changed indexOf("/") to lastIndexOf("/") so think-mode correctly extracts the base model name
  from multi-slash IDs.
• Model resolution pipeline (src/shared/model-resolution-pipeline.ts): Replaced naive [parts[0]] provider hint extraction at 4 sites with extractProviderHint
  validated against connected providers.
• Delegate-task model selection (src/tools/delegate-task/model-selection.ts): Same extractProviderHint fix for the category-default and user fallback model paths.
• call-omo-agent model forwarding (src/tools/call-omo-agent/tools.ts, sync-executor.ts, background-executor.ts): Added resolveModelForCallOmoAgent to read
  agent override model from config, and pass model/variant in the promptAsync body and manager.launch() call -- matching how delegate-task already handles this.

Testing

bun run typecheck        # Clean
bun test                 # 2514 pass, 3 pre-existing failures (jest.clearAllTimers in unrelated files)
                                                                                                                                                                          
New test coverage for multi-slash model ID handling in:                                                                                                                   
- src/shared/extract-provider-hint.test.ts                                                                                                                                
- src/shared/model-availability.test.ts                                                                                                                                   
- src/shared/model-resolution-pipeline.test.ts                                                                                                                          
- src/tools/delegate-task/model-selection.test.ts                                                                                                                         
- src/hooks/think-mode/switcher.test.ts 

<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Adds robust support for multi-slash model IDs and forwards user-selected models to sub-agents, including inheriting model/variant from user categories. This prevents unintended fallbacks and keeps sub-agent runs aligned with user-selected models.

- **New Features**
- Extracts a validated provider hint from model strings using connected providers; supports IDs like `aws/anthropic/bedrock-claude-opus-4-6` when the first segment isn’t a real provider.
- `fuzzyMatchModel` retries without the provider filter if no candidates remain after filtering, enabling cross-provider resolution.
- For `call-omo-agent`, forwards the configured `model` and optional `variant` to both sync and background executors, and inherits them from user categories when the override references a category.

- **Bug Fixes**
- Think-mode now uses the last slash to extract the base model, so high-variant logic works with multi-slash IDs.
- Model resolution and delegate-task selection use validated provider hints instead of naive splitting, fixing multi-slash category defaults and user fallbacks.

<sup>Written for commit b6bc1a24a5945e551b93ae5f238aa673bb947826. Summary will update on new commits.</sup>

<!-- End of auto-generated description by cubic. -->

[github-actions]

All contributors have signed the CLA. Thank you! ✅
_{Posted by the CLA Assistant Lite bot.}

[hunghoang3011]

I have read the CLA Document and I hereby sign the CLA

[cubic-dev-ai]

3 issues found across 14 files

Confidence score: 3/5

• There is a concrete regression risk in src/tools/call-omo-agent/tools.ts: model resolution currently skips category-level inheritance and only uses agentOverride.model, which can cause the wrong primary model to be selected at runtime.
• The other findings in src/shared/model-resolution-pipeline.ts and src/shared/model-availability.ts are lower severity (duplicate/shadowed initialization and unreachable fallback branch) and are more about correctness clarity and maintainability than immediate breakage.
• Given one medium-severity, high-confidence user-facing behavior issue plus a couple of minor refactor artifacts, this carries some merge risk but is likely manageable with a focused fix.
• Pay close attention to src/tools/call-omo-agent/tools.ts, src/shared/model-resolution-pipeline.ts, src/shared/model-availability.ts - ensure inheritance-based model selection is restored and clean up shadowed/dead fallback logic.

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="src/shared/model-resolution-pipeline.ts">

<violation number="1" location="src/shared/model-resolution-pipeline.ts:49">
P2: Refactor introduced duplicate `connectedProviders` initialization; inner fallback-chain declaration shadows outer variable and redundantly re-reads cache.</violation>
</file>

<file name="src/tools/call-omo-agent/tools.ts">

<violation number="1" location="src/tools/call-omo-agent/tools.ts:51">
P2: `call-omo-agent` model resolution ignores category-level model inheritance and only reads `agentOverride.model`, so category-configured primary models are silently skipped.</violation>
</file>

<file name="src/shared/model-availability.ts">

<violation number="1" location="src/shared/model-availability.ts:68">
P3: The added `else` branch in the empty-candidates fallback is dead code and cannot be reached with current control flow.</violation>
</file>

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[cubic-dev-ai]

0 issues found across 4 files (changes from recent commits).

_{Auto-approved: Fixes multi-slash model resolution and adds model forwarding to sub-agents. Changes are well-tested and improve robustness of provider/model mapping.}