docs: drop retired full-graph settings and model keys

[sami-marreed]

Documentation Pull Request

Related Issue

none

Description

Remove documentation for settings and model keys that were deleted from cuga-agent when the full CugaAgent graph was retired. Keep CugaLite, CugaSupervisor, and remaining live knobs. Document cuga_mode as a code generation profile (fast | balanced | accurate | custom) rather than a reasoning mode.

Type of Changes

• Documentation update
• New documentation
• Documentation fix/correction
• README update
• API documentation
• Code comments/docstrings

Changes Made

• Strip retired [features] / [advanced_features] / [evolve] keys from the settings sample, option tables, recipes, and troubleshooting (save_reuse_fast, lite_mode, lite_mode_tool_threshold, force_lite_mode_apps, api_planner_hitl, code_planner_enabled, save_reuse_generate_html, decomposition_strategy, use_paraphrase, use_location_resolver, sub_task_keep_last_n, evolve.lite_mode_only)
• Drop the Workflow Options table; keep saved_flows as the internal ChatAgent SSE helper port
• Align model examples with the six remaining roles (planner, chat, final_answer, code, qa, action) and keep the reasoning-high profiles
• Remove the Knowledge CugaLite routing section; keep the awareness-block callout
• Remove lite_mode / lite_mode_only from the Memory enable snippet and tuning table; keep [evolve]
• Stop citing api_planner.md on the special-instructions stub

Verification

• I have reviewed the documentation for accuracy
• I have checked for spelling and grammar errors
• Links and references are working correctly
• Code examples (if any) have been tested

Checked against cuga-agent e715d6436ec98eea5ce6607729047ab2b9e4d12e (settings.toml and configurations/models/settings.openai.toml). Save-reuse URL stubs are unchanged.

Checklist

• My documentation follows the project's documentation style
• I have performed a self-review of my changes