docs: archival/standalone notes for vendored third_party assets

docs/TTS-DESIGN.md

@@ -393,8 +393,20 @@ not need to parse or implement them:
 
 ### Paths and configuration (standalone)
 
-The engine project is standalone: it has no path dependency on Veskslop and only a
-default sibling-directory dependency on the asset checkouts, both overridable.
+The engine project is standalone and archival: it has no path dependency on Veskslop,
+and every non-installable dependency is vendored under `third_party/`, so nothing is
+fetched from the network at build or run time:
+
+- `third_party/speech.h` — SAPI4 SDK header used by the build.
+- `third_party/sapi4/` — SAPI4 runtime (`SPEECH.DLL` + INF), MSTTS engine + voices,
+  and the original installers.
+- `third_party/flextalk/data1.cab` — AT&T Flextalk installer (Keith Bell / Kerry Watson).
+- `third_party/nettss-reference/` — NetTTS VOX parser source, kept to validate
+  `setup/vox_parser.py`.
+
+Only toolchain packages are installed by `setup/install-deps.sh` (Wine/Winelib, ffmpeg,
+python3, unshield, mingw). Everything else lives in the repository.
+
 `setup/install.sh` writes `setup/microslopsam.env` with absolute paths; environment
 variables take precedence over that file, so anything can be relocated without editing
 scripts:
@@ -411,16 +423,16 @@ scripts:
 | `MICROSLOP_WINE` / `_XVFB` / `_PYTHON` / `_FFMPEG` | tool names | tool overrides |
 
 The wrapper needs only `VESKSLOP_TTS_CMD` to point at its absolute path; it derives
-everything else from its own location plus the env file. `speech.h` is vendored in
-`third_party/`, so the build no longer needs the SDK checkout.
+everything else from its own location plus the env file.
 
 ### Merging into Veskslop
 
 This tree is written to survive a copy into the Veskslop repository next to its daemon:
 
-1. Copy `microslopsam/` (or replace the existing copy), then refresh the configuration:
-   `MICROSLOP_UPDATE_ENV=1 microslopsam/setup/install.sh`. Re-running install is
-   idempotent; it rewrites `setup/microslopsam.env` for the new absolute paths.
+1. Copy `microslopsam/` (or replace the existing copy). The vendored assets under
+   `third_party/` come along, so the merged tree stays self-contained. Then refresh the
+   configuration: `MICROSLOP_UPDATE_ENV=1 microslopsam/setup/install.sh`. Re-running
+   install is idempotent; it rewrites `setup/microslopsam.env` for the new absolute paths.
 2. No daemon changes are required. The env/placeholder contract is unchanged
    (`VESKSLOP_TTS_*`, `{out}`, `{text_file}`, voice/speed/pitch/expression/profile/
    highpass/echo/words/word_gap_ms). New features are additive and default off.