fix(model): rearchitect how model and providedr information is stored

[tusharmath]

• chore(ISSUE_TEMPLATE): streamline bug report fields
• feat(ui): add workspace init confirmation before syncing (feat(ui): add workspace init confirmation before syncing #2822)
• feat(provider): add Google AI Studio support (chore(provider): add Google AI Studio support #2805)
• feat(auth): add OAuth authorization code + PKCE for Codex provider (feat(auth): add OAuth authorization code + PKCE for Codex provider #2790)
• chore(deps): bump the major group across 1 directory with 5 updates (chore(deps): bump the major group across 1 directory with 5 updates #2783)
• fix(bedrock): sanitize tool call IDs for Anthropic compatibility (fix(bedrock): sanitize tool call IDs for Anthropic compatibility #2837)
• fix(sync): exclude symlinked files from discovery results (fix(sync): exclude symlinked files from discovery results #2849)
• fix: correct token double-counting for Anthropic and Bedrock providers (fix: correct token double-counting for Anthropic and Bedrock providers #2861)
• fix: atomic provider and model selection with proper cancellation handling (fix: atomic provider and model selection with proper cancellation handling  #2803)
• refactor(config): read ForgeConfig once at startup and thread it through the stack (refactor(config): read ForgeConfig once at startup and thread it through the stack #2850)
• fix(app): return error when conversation is not found (fix(app): return error when conversation is not found #2852)
• fix(ui): allow model selection when provider activation completes without selection (fix(ui): allow model selection when provider activation completes without selection #2863)
• chore(alias): add 'provider' alias for provider-login commandchore (chore(alias): add 'provider' alias for provider-login commandchore #2865)
• feat(config): allow configuration of the base_path (feat(config): allow configuration of the base_path #2864)
• chore(auth): add warning for Claude Code provider about account ban risk (chore(auth): add warning for Claude Code provider about account ban risk #2838)
• fix(http): append debug request body chunks instead of overwriting (fix(http): append debug request body chunks instead of overwriting #2875)
• feat(tools): add multi_patch tool for batch file edits (feat(tools): add multi_patch tool for batch file edits #2840)
• docs(README): add newcomer orientation, ZSH plugin reference, and sync CLI docs (docs(README): add newcomer orientation, ZSH plugin reference, and sync CLI docs #2862)
• feat: subagent as task (feat: subagent as task #2508)
• chore(ci): add release-drafter autolabel for provider.json
• chore(skill): add resolve-fixme skill to find and triage FIXME (chore(skill): add resolve-fixme skill to find and triage FIXME #2876)
• chore(config): make provider_id and model_id required
• chore(config): require provider model fields and set atomically!

[tusharmath]

Drop the setters and getters for default model also from api. Update the implementation to use only the model+provider selector to select them atomically.