v1.3.0: Bedrock translator refactor, usage metrics, session restore fixes, and predefined rules

Major changes:

- **Bedrock translator architecture**: Extract orchestration logic from `impl.rs` into
  a dedicated `translator.rs` module. Rename `convert_request.rs` → `request_translator.rs`
  and `stream.rs` → `response_translator.rs` for clarity. Remove `tool_docs.rs` (inlined).
  Remove `fallback_to_warp` setting and server fallback path — Bedrock is now the sole backend.

- **Unknown tool handling**: The response translator now detects hallucinated/unknown tool
  calls from the model and synthesizes error tool_results so the conversation doesn't
  deadlock waiting for a result that will never come.

- **Usage display overhaul**: Replace credit-based usage display with detailed token metrics
  showing context window %, cache hit rate (read/write/miss), and estimated cost in dollars.
  Add `total_input_tokens`, `total_cache_read_tokens`, `total_cache_write_tokens`, and
  `cache_miss_tokens` accessors to `AIConversation`.

- **Predefined rules system**: Add `predefined_rules.rs` with 11 system-defined behavioral
  rules that are auto-seeded on first launch. Add "Add Predefined Rules" button to the
  Rules UI for re-adding them later. Track seeding state via `has_seeded_predefined_rules`
  setting.

- **Session restore improvements**: Rename database file from `warp.sqlite` to
  `galaxy.sqlite` with automatic migration from both same-directory and state_dir legacy
  paths. Improve CWD persistence by falling back to `session_startup_path` for agent-mode
  and fresh tabs. Add extensive session-save/restore logging.

- **Shell bootstrap rebrand**: Rename `WARP_INITIAL_WORKING_DIR` environment variable to
  `GALAXY_INITIAL_WORKING_DIR` across bash, zsh, and fish bootstrap scripts.

- **Model defaults**: Change default Bedrock model from Opus 4.7 to Opus 4.6.
  Add `context_window_for_model()` helper with model-aware context sizes.
  Remove `is_bedrock_model()` (no longer needed without server fallback).

- **User query persistence**: The response translator now emits a `UserQuery` proto message
  at stream start so the user's prompt persists across sessions for conversation titles.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/src/settings_view/ai_page.rs

@@ -2081,7 +2081,6 @@ pub enum AISettingsPageAction {
     SetBedrockAuthMethod(BedrockAuthMethod),
     SetBedrockProfile(String),
     ToggleBedrockCrossRegionInference,
-    ToggleBedrockFallbackToWarp,
     ToggleFileBasedMcp,
     ToggleIncludeAgentCommandsInHistory,
     ToggleAgentAttribution,
@@ -2742,7 +2741,6 @@ impl TypedActionView for AISettingsPageView {
                         access_key_id: ai_settings.bedrock_access_key_id.value().clone(),
                         secret_access_key: ai_settings.bedrock_secret_access_key.value().clone(),
                         cross_region_inference: *ai_settings.bedrock_cross_region_inference.value(),
-                        fallback_to_warp: *ai_settings.bedrock_fallback_to_warp.value(),
                     }.with_external_fallbacks();
 
                     ctx.spawn(
@@ -2781,12 +2779,6 @@ impl TypedActionView for AISettingsPageView {
                 });
                 ctx.notify();
             }
-            AISettingsPageAction::ToggleBedrockFallbackToWarp => {
-                AISettings::handle(ctx).update(ctx, |settings, ctx| {
-                    report_if_error!(settings.bedrock_fallback_to_warp.toggle_and_save_value(ctx));
-                });
-                ctx.notify();
-            }
             AISettingsPageAction::ToggleFileBasedMcp => {
                 AISettings::handle(ctx).update(ctx, |settings, ctx| {
                     report_if_error!(settings.file_based_mcp_enabled.toggle_and_save_value(ctx));