refactor(app): the device's speech recognition moves from Learn into halkyon_app, with dictation into a text

Learn's `SpeechInput` and `DeviceSpeechInput` (ADR 0021, D67) are
halkyon_app's now, and its `FakeSpeechInput` is in `testing.dart`, so
Meditate's dream journal (ADR 0038, D15) listens through the same code.
Learn imports them from there and behaves as before: its composer and
its tests are unchanged but for the imports, and `DeviceSpeechInput()`
asks for what it asked before.

`DeviceSpeechInput` takes three options, off by default:
- `preferOnDevice`: on Android, recognition on the device where it can
  (Android 12 on), else offline; should that fail before a word is
  heard (not a pause), it listens as Android otherwise does from then
  on.
- `pauseFor`: how long a pause may last before the recogniser stops.
- `listenFor`: how long one listen may last at most.

`Dictation` writes what is heard where the cursor stands
(`DictationInsertion`: in place of a selection, set apart by a space),
shows the words so far, and listens again after each pause while it is
on, stopping by itself after three listens running heard nothing.

speech_to_text moves from Learn's pubspec to halkyon_app's, the lock
unchanged. Todo, Train and Meditate link the plugin now; their
generated plugin registrants (macOS, Windows) say so. An app declares
the microphone itself, and Todo and Train declare none, so nothing
there can listen.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

AGENTS.md

@@ -10,7 +10,7 @@ Halkyon's apps and the packages they share, in one repository and one pub worksp
 - **`packages/`**: what the apps share, each with its README and licence, which the apps take by path (`path: ../../../packages/<package>`), so a change to a shared package and to the apps using it is one commit:
   - `halkyon_ui`: Halkyon's look, the theme around cobalt and copper, Noto Sans bundled, the window-size classes and the widgets every screen is built of (the floating bar and rail, `FoldingTabs`' tab row folding into the title), with texts of its own (English, German).
   - `halkyon_base_server`, `halkyon_base_client`: the Serverpod module every Halkyon server includes (ADR 0014): signing in (a password with TOTP and the resets of ADR 0017, SimpleLogin on `halkyon_oidc`, email codes proving an address; no anonymous accounts since ADR 0020, D25, nor GitHub since D36), an account's ways in and its deletion with a hook for each app's own data, the pruning, the instance's basics, people's handles and public profiles, who may sign up (`SIGN_UP`: open, approval, closed) with the accounts waiting for approval and the instance's operators who approve them (Halkyon Learn's ADR 0021, step 1), the operator's assistants forwarded on halkyon_llm with their grants, each person's budget, the efforts they allow and counted figures, and the instance's privacy page made from its settings (step 2), and the instance's register (ADR 0016): one account per person across an operator's services, held by one service (Learn's server on learn.halkyon.eu) and asked by the others, its members (`ACCOUNT_REGISTER_URL`), all sharing a secret (`INSTANCE_SECRET`); its README says how.
-  - `halkyon_app`: every app's shell on the module's client (ADR 0014): the instances a device keeps accounts on and the first start, signing in and switching person, the gates building an app's dependencies per instance and per person, the sync service and where it stands, the account section of an app's settings (`AccountTiles`), every app's Profile (`HalkyonProfile`, decided 2026-11-02: the person's own tab, the same in every app, with their account, the ways they sign in and their public profile, one for all apps, then the app's own tabs) and people's public profiles (`PublicProfileRepository`, `PublicProfileSection`, `showProfileOf`), the wait screen of an account waiting for approval and the operator's card, badge and screen (ADR 0021), the assistants of an app's settings (`AssistantsCard`: granted, by provider, agreed to, what is left of the person's budget, used, and the person's own keys) and the operator's grants from that screen (`AssistantGrantsScreen`: several assistants to several people at once, each with one budget, D57 to D63), with the repositories asking them through the module, at an effort the operator allows, or a person's own key directly (step 2) and what an app's warning before a private studyset goes names (`providerTermsOf`, `OwnAssistant.onThisMachine`, step 3), About with the instance's source link (`showAppAbout`), what's new after an update (`WhatsNew`, `WhatsNewOnUpdate`, `WhatsNewTile`, from the app's `assets/whats_new/`, Train's ADR 0030, D61), the language every app picks (`resolveAppLocale`) and countries' and subdivisions' names (Unicode CLDR's, bundled), with texts that name the app.
+  - `halkyon_app`: every app's shell on the module's client (ADR 0014): the instances a device keeps accounts on and the first start, signing in and switching person, the gates building an app's dependencies per instance and per person, the sync service and where it stands, the account section of an app's settings (`AccountTiles`), every app's Profile (`HalkyonProfile`, decided 2026-11-02: the person's own tab, the same in every app, with their account, the ways they sign in and their public profile, one for all apps, then the app's own tabs) and people's public profiles (`PublicProfileRepository`, `PublicProfileSection`, `showProfileOf`), the wait screen of an account waiting for approval and the operator's card, badge and screen (ADR 0021), the assistants of an app's settings (`AssistantsCard`: granted, by provider, agreed to, what is left of the person's budget, used, and the person's own keys) and the operator's grants from that screen (`AssistantGrantsScreen`: several assistants to several people at once, each with one budget, D57 to D63), with the repositories asking them through the module, at an effort the operator allows, or a person's own key directly (step 2) and what an app's warning before a private studyset goes names (`providerTermsOf`, `OwnAssistant.onThisMachine`, step 3), About with the instance's source link (`showAppAbout`), the device's own speech recognition (`SpeechInput`, `DeviceSpeechInput` on `speech_to_text`, `FakeSpeechInput` in `testing.dart`; none on Linux) and dictation into a text at its cursor, listening again after each pause (`Dictation`, Meditate's ADR 0038, D15; an app that listens declares the microphone and its usage texts itself), what's new after an update (`WhatsNew`, `WhatsNewOnUpdate`, `WhatsNewTile`, from the app's `assets/whats_new/`, Train's ADR 0030, D61), the language every app picks (`resolveAppLocale`) and countries' and subdivisions' names (Unicode CLDR's, bundled), with texts that name the app.
   - `halkyon_core` (low-level primitives in pure Dart: ids, a logger, `SerialQueue`, `CoalescingRunner`) and `halkyon_interop` (contracts between apps, pure Dart).
   - `halkyon_keys` (pure Dart on libsodium, ADR 0017): an account's keys on the device, the password's Argon2id and SRP's x, the key pairs and their wrapping, the recovery phrase, data keys, content sealed and signed, row IDs keyed by the account (`keyedRowId`). SRP-6a's two halves are the module's (`halkyon_base_server`'s `base.dart`, `halkyon_base_client`'s `srp.dart`), as are TOTP and the recovery codes. `sodium`'s build hook compiles libsodium, so every machine that builds or tests needs a C compiler and `make`.
   - `halkyon_llm` (pure Dart, Halkyon Learn's ADR 0021, D15 and D46): language models' APIs streamed over plain HTTP, no SDKs: Anthropic's Messages API, OpenAI's chat completions (each known host's fields, D45) and its Responses API, behind one interface (`LlmClient`), with `FakeLlmClient` for tests; tested on replies written from the providers' documentation and on those `tool/record_llm.dart` records with a key (D36). The module forwards the operator's assistants with it, and the apps call a person's own provider. BSD-3-Clause as `halkyon_oidc`, `publish_to: none`.