Per-chat reasoning effort in contextual sheet

[YoussefKeyrouz]

Task/Issue URL: https://app.asana.com/1/137249556945/project/1212810093780571/task/1215062229903137?focus=true

Description

Wires the contextual Duck.ai sheet into the per-chat reasoning flow introduced by #8666 and fixes two correctness bugs

• Minor cleanup in ReasoningModePickerViewModel

Steps to test this PR

Per-chat scope restored on reopen

• Start a chat in the contextual sheet on tab A; pick a non-default model and reasoning effort; submit a prompt.
• Close the contextual sheet.
• Open new duck ai on another tab or submit a prompt via the native input field using a new model (global default changes)
• Reopen the contextual sheet on tab A (within the session window). Verify the picker reflects the reasoning effort, not the global default)
• Submit another prompt; confirm that the submission carries the chat's modelId and reasoningEffort.
• Open another tab and start a new chat in the contextual sheet on tab B
• Switching between tabs properly restore the reasoning effort of the corresponding chat.

Globals untouched

• After any per-chat submission above, dismiss the sheet and open Duck.ai from the address bar (or a fresh tab). Verify your global defaults are unchanged.

---

Note

Medium Risk
Moderate risk: changes how the contextual sheet tracks/propagates the active chatId, which affects session restore behavior and per-chat model/reasoning selection; regressions could surface as incorrect picker state or chat continuity issues.

Overview
Adds a chatId state flow to DuckChatContextualViewModel, derived from the current/stored Duck.ai URL, and keeps it in sync whenever the sheet URL changes or a new chat is started.

Wires this chatIdFlow through DuckChatContextualFragment into ContextualNativeInputManager/NativeInputModeWidget so native input can participate in per-chat reasoning/model scoping when reopening/restoring contextual chats. Includes a small correctness/cleanup tweak in ReasoningModePickerViewModel to use a single modelState snapshot per tap, plus new unit tests covering chatId lifecycle (set on restore/load, unchanged in INPUT mode, cleared on new chat).

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[YoussefKeyrouz]

• Per-chat reasoning effort in contextual sheet #8674 👈 (View in Graphite)
• Per-chat model and reasoning restoration on existing Duck.ai chats. #8666
• Publish active chatId to NativeInputState (per-tab) #8664
• develop

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[malmstein]

tested locally and confirmed it works as expected.

clean wire-up of contextual into the per-chat reasoning flow. nice that this PR also fixes the fullModeUrl correctness gap on the existing-chat-restore and new-chat-clear paths — easy to miss those were never being assigned before. the ReasoningModePickerViewModel.onModeTapped snapshot of modelState is a small but real win against the chance of a fetchModels emission landing mid-handler.

main note is the fullModeUrl / _chatId pair-assignment drift risk below. separately worth keeping on the radar: PR #8631 (still open) adds Uri.toChatIdOrNull(duckChat) in duckchat-api doing similar parsing — once it lands, both this PR's extractChatId and any other in-flight extractors could converge on the api extension. not blocking either way.

note for outcome tracking: the model-fallback asymmetry I flagged on #8666 (L161, getSelectedModelId vs getResolvedReasoningEffort when chat's model isn't in modelState) isn't touched here — that one's still pending on #8666's side.

[malmstein]

nit: fullModeUrl = ...; _chatId.value = extractChatId(...) is now repeated at L190-191, L243-244, and L289+292 (and a clearing pair at L649-650). a future addition that sets a new sheet URL but forgets the chatId update would silently break per-chat resolution. can we wrap this in a private helper like setSheetUrl(url: String?) that owns both fields, plus a clearSheetUrl() for the new-chat path? keeps the invariant in one place.

[YoussefKeyrouz]

Good catch. Addressed.

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