fix(config): honor a configured default_text_model; align the unset default with deepseek-flash

The V4.1 change moved the DeepSeek default to deepseek-flash but left two
paths disagreeing:

- Route/thread resolution ignored an operator-configured
  default_text_model and fell through to the provider catalog default, so
  a config declaring default_text_model = "deepseek-v4-pro" created new
  threads on flash (runtime_threads::create_thread ->
  resolve_runtime_route_for_identity with no selector).
- The TUI DEFAULT_TEXT_MODEL still said deepseek-v4-pro, so a bare config
  reported one default and routed another.

Resolution now mirrors provider_default_model precedence: the active
provider configured default wins over the provider catalog default. The
constant moves to deepseek-flash, matching DEFAULT_DEEPSEEK_MODEL in
codewhale-config and the shipped default.

The composed-frame test now pins the #6041 contract: the duplicate session
reading is suppressed on a first turn and returns once a finished turn
makes the totals differ.

Evidence (each: 1 passed; 0 failed):
- config::tests::remembered_deepseek_cn_and_layered_root_models_keep_their_precedence
- doctor_endpoint_tests::doctor_api_target_reports_default_endpoint
- doctor_endpoint_tests::doctor_api_target_routes_deepseek_cn_alias_to_beta_endpoint
- runtime_api::configured_model_api_tests::scoped_runtime_selections_leave_device_memory_unchanged
- runtime_api::tests::fleet_status_runtime_api_exposes_state_and_actions
- tui::ui::frame::one_owner_tests::composed_frame_paints_each_fact_in_exactly_one_row
- tui::ui::tests::provider_switch_to_deepseek_canonicalizes_openrouter_default_model
- tui::ui::tests::provider_switch_to_deepseek_drops_stale_xiaomi_root_base_url

crates/tui/src/config/models.rs

@@ -6,7 +6,7 @@
 //! re-exported from `crate::config` via `pub use models::*;`, so every existing
 //! `crate::config::<CONST>` path keeps resolving unchanged (#3311).
 
-pub const DEFAULT_TEXT_MODEL: &str = "deepseek-v4-pro";
+pub const DEFAULT_TEXT_MODEL: &str = "deepseek-flash";
 pub const DEFAULT_DEEPSEEK_BASE_URL: &str = "https://api.deepseek.com/beta";
 pub const DEFAULT_DEEPSEEK_ANTHROPIC_MODEL: &str = DEFAULT_TEXT_MODEL;
 pub const DEFAULT_DEEPSEEK_ANTHROPIC_BASE_URL: &str = "https://api.deepseek.com/anthropic";

crates/tui/src/route_runtime.rs

@@ -748,7 +748,19 @@ pub(crate) fn resolve_runtime_route_for_identity(
     )?;
     let provider = identity.provider;
     let mut route_config = prepared_route_config(config, &identity, model_selector);
-    let saved_provider_model = configured_model_for_route(&route_config, provider);
+    // The operator's effective default for the active provider is the
+    // route's default too; mirror `provider_default_model` precedence so a
+    // configured choice is not displaced by the provider catalog's default
+    // (deepseek-flash). `auto` stays the resolver's sentinel.
+    let configured_default = (provider == config.api_provider()
+        && config.default_text_model.is_some())
+    .then(|| config.default_model())
+    .filter(|model| {
+        let model = model.trim();
+        !model.is_empty() && !model.eq_ignore_ascii_case("auto")
+    });
+    let saved_provider_model = configured_model_for_route(&route_config, provider)
+        .or(configured_default.as_deref());
     // #5034: with no explicit selector and no saved model, a Codex route
     // would fall back to the resolver's static seed offering. Prefer the
     // live Codex roster head so a provider switch lands on the current

crates/tui/src/tui/ui/frame/one_owner_tests.rs

@@ -211,20 +211,43 @@ fn composed_frame_paints_each_fact_in_exactly_one_row() {
         // session half needs 120 columns here, the turn half 160. Each
         // paints in exactly one row wherever it paints. The metrics line
         // carries no repository, branch or provider.
-        let clock_facts: &[(u16, &str)] =
-            &[(120, "worked 1m 15s"), (160, "sub-agents underway 1m 15s")];
-        for (needs, needle) in clock_facts {
-            if width < *needs {
-                continue;
-            }
-            assert!(rows[posture].contains(needle), "{}", rows[posture]);
+        // First turn: the turn half names the phase and stays; the session
+        // reading is the identical duration, so it is suppressed rather than
+        // stated twice (#6041) — the turn half is the one that needs 160
+        // columns, so a narrower row keeps the affordances and no stopwatch.
+        let turn_needle = "sub-agents underway 1m 15s";
+        if width >= 160 {
+            assert!(rows[posture].contains(turn_needle), "{}", rows[posture]);
             assert_eq!(
-                count_rows_containing(&rows, needle),
+                count_rows_containing(&rows, turn_needle),
                 1,
-                "{width}x{height}: {needle:?} paints in exactly one row:\n{}",
+                "{width}x{height}: {turn_needle:?} paints in exactly one row:\n{}",
                 rows.join("\n")
             );
         }
+        assert!(
+            !rows[posture].contains("worked 1m 15s"),
+            "{width}x{height}: the duplicate session reading must not be stated: {}",
+            rows[posture]
+        );
+        // After a finished turn the totals differ and the worked chip
+        // returns: 1m of finished turns plus the live 1m 15s reads 2m 15s.
+        let mut worked = working_app();
+        worked.cumulative_turn_duration = Duration::from_secs(60);
+        let rows = draw(&mut worked, width, height);
+        if width >= 120 {
+            let worked_needle = "worked 2m 15s";
+            assert!(rows[posture].contains(worked_needle), "{}", rows[posture]);
+            assert_eq!(
+                count_rows_containing(&rows, worked_needle),
+                1,
+                "{width}x{height}: {worked_needle:?} paints in exactly one row:\n{}",
+                rows.join("\n")
+            );
+        }
+        if width >= 160 {
+            assert!(rows[posture].contains(turn_needle), "{}", rows[posture]);
+        }
         assert!(!rows[metrics].contains('⑂'), "{}", rows[metrics]);
         // No dead key hints anywhere in the frame.
         for row in &rows {