fix(bookplayer): keep audio stream open across page turns + fade-in/out

Close and re-creating the codec on every page change caused an audible pop
between pages. Now open_output_stream reuses an already-open stream when the
format matches, the codec is left open on a natural page finish (only torn
down on user stop / back / app close), and a short fade-in/out is applied at
each page boundary. Also fixes pre-existing device API renames (device_find_*
-> device_get_* out-param style).

Docs: record where the Tactility SDK actually lives and that the fresh CDN
0.8.0-dev SDK is broken for this setup (app-module resolution), with the
cached working copy workaround.

AGENTS.md

@@ -9,23 +9,42 @@ Tactility external ELF apps — loaded at runtime via firmware symbol table. Eac
 Upstream: `https://github.com/TactilityProject/TactilityApps`
 Personal Gitea mirror: `https://git.reynafamily.com/adolforeyna/tactility_apps` (`personal` remote)
 
-Dev board IP: `192.168.68.112` (S3, OS 0.8.0-dev, SDK 0.8.0-dev) — main deploy target. `.111` also online. OS image is 0.8.0-dev so manifest should use `sdk=0.8.0-dev` or loader warns.
+Dev board IP: `192.168.68.112` (S3, OS 0.8.0-dev, SDK 0.8.0-dev) — main deploy target. `.111` and `.114` also online. OS image is 0.8.0-dev so manifest should use `sdk=0.8.0-dev` or loader warns.
 
 ## Local Workstation
 
-- Host: M2 Air (14,2) macOS 26.5.2
-- Project: `/Users/adolforeyna/Projects/Tactility/apps`
-- ESP-IDF: `/Users/adolforeyna/esp/esp-idf`, Python env `idf5.3_py3.9_env` at `~/.espressif/python_env/idf5.3_py3.9_env`
-- Tactility SDK: `/Users/adolforeyna/Projects/Tactility/firmware/release/TactilitySDK` (built locally, `--local-sdk`)
+- Host: macOS 26.5.2
+- Project: `/Users/adolforeyna/Projects/electronics/tactility/tactility_apps`
+- ESP-IDF: `/Users/adolforeyna/esp/esp-idf` (v5.5.2), Python env `idf5.5_py3.9_env` at `~/.espressif/python_env/idf5.5_py3.9_env` (NOT `idf5.3_py3.9_env` — that env does not exist on this machine)
+
+### Tactility SDK location (IMPORTANT)
+
+- When you run `tactility.py ... build` **without** `--local-sdk`, it auto-downloads the SDK to the per-app cache:
+  `Apps/<Name>/.tactility/<version>-<platform>/TactilitySDK` (e.g. `Apps/BookPlayer/.tactility/0.8.0-dev-esp32s3/TactilitySDK`).
+- **The freshly CDN-downloaded 0.8.0-dev SDK for esp32s3 is broken for this setup** — it fails at CMake with
+  `Failed to resolve component 'app-module' required by component 'TactilitySDK': unknown name` and also renames the
+  device API (`device_find_*` → `device_get_by_name/device_get_first_by_type` out-param style). It is a *different,
+  newer* SDK than the working one.
+- **The known-good SDK is the locally-cached copy** already present in the other apps'
+  `.tactility/0.8.0-dev-esp32s3/TactilitySDK` (the one that carries a `Drivers/` folder). It builds clean.
+- Workaround when a fresh download fails: copy the working cached SDK over the broken one:
+  ```bash
+  SRC=Apps/PipecatVoice/.tactility/0.8.0-dev-esp32s3   # known-good copy
+  DST=Apps/MyApp/.tactility/0.8.0-dev-esp32s3
+  rm -rf "$DST/TactilitySDK"; cp -R "$SRC/TactilitySDK" "$DST/"
+  ```
+  Then rebuild. (Resolving the root cause on the newer SDK is still TODO — consider pinning/downloading the cached zip
+  so this isn't needed per-app.)
 
 ### Hardware
 
 | Board | IP | Port | Notes |
 |-------|-----|------|-------|
 | ES3C28P 2.8" color 240x320 | `192.168.68.112` | `/dev/cu.usbmodem101` | Primary deploy target, 16MB flash, OCT PSRAM, SD for ELF assets |
-| Waveshare RLCD 4.2" mono 400x300 ST7305 | `192.168.68.111`? .1101 USB | `/dev/cu.usbmodem1101` | Secondary, compact density, mono threshold 60, font 18 |
+| ES3C28P 2.8" color 240x320 | `192.168.68.114` | `/dev/cu.usbmodem101` | Secondary S3 (used for recent BookPlayer deploys) |
+| Waveshare RLCD 4.2" mono 400x300 ST7305 | `192.168.68.111` | `/dev/cu.usbmodem1101` | Secondary, compact density, SD threshold 60, font 18 |
 
-User shorthand: "ending in 112" → `192.168.68.112`.
+User shorthand: "ending in 112" → `192.168.68.112`. Install is dashboard-port API (80), not dev port 6666.
 
 ## Build, Deploy, Run — Correct Env Wrapper
 
@@ -34,11 +53,10 @@ Hermes desktop Python 3.11 venv pollutes `PYTHONPATH` → `tactility.py` crashes
 Always:
 
 ```bash
-cd /Users/adolforeyna/Projects/Tactility/apps
+cd /Users/adolforeyna/Projects/electronics/tactility/tactility_apps
 unset PYTHONPATH; unset PYTHONHOME
-export IDF_PYTHON_ENV_PATH=/Users/adolforeyna/.espressif/python_env/idf5.3_py3.9_env
+export IDF_PYTHON_ENV_PATH=/Users/adolforeyna/.espressif/python_env/idf5.5_py3.9_env
 source /Users/adolforeyna/esp/esp-idf/export.sh
-export TACTILITY_SDK_PATH=/Users/adolforeyna/Projects/Tactility/firmware/release/TactilitySDK
 
 # Build
 $IDF_PYTHON_ENV_PATH/bin/python tactility.py Apps/MyApp clean