Cleanup: stale mistral:7b-instruct references after model change to qwen3.5:9b (#2383)

[mrveiss]

Problem

PR #2383 changed DEFAULT_LLM_MODEL from mistral:7b-instruct to qwen3.5:9b, but stale references remain throughout the codebase.

Discovered During

Rebase conflict resolution for #2383 on Dev_new_gui.

Affected Files

Code (5 occurrences in autobot-shared/ssot_config.py):

• Line 231: docstring example 'mistral:7b-instruct'
• Line 319: docstring example 'mistral:7b-instruct'
• Line 901: inline comment # mistral:7b-instruct
• Line 1226: docstring example AUTOBOT_ORCHESTRATOR_MODEL=mistral:7b-instruct
• Line 1309: f-string example mistral:7b-instruct

Documentation (20+ occurrences):

• docs/api/environment-variables.md (3 refs)
• docs/ROADMAP_2025.md (5 refs)
• docs/architecture/EFFICIENT_INFERENCE_DESIGN.md (5 refs)
• docs/architecture/SSOT_CONFIGURATION_ARCHITECTURE.md (4 refs)
• docs/developer/DISTRIBUTED_TRACING.md (1 ref)
• autobot-infrastructure/shared/analysis/ reports (3 refs)

Backups (can ignore):

• backups/refactoring/chat_workflow_manager_*.py (3 refs)

Fix

Replace mistral:7b-instruct with qwen3.5:9b (or a generic placeholder like DEFAULT_LLM_MODEL) in all docstrings, comments, and documentation files. Leave backup files as-is.

Impact

Low — cosmetic/documentation only. No runtime behavior affected.

[mrveiss]

Merged in PR #2470.