chore: delete scripts/ and cut requirements.txt down to its real consumers

scripts/ held the pre-marketplace MCP servers (gmail, gcal, gmaps, ssh, weather,
google_trends, whatsapp, serpapi_flights). Nothing referenced them any more:
connectors are admin-curated and installed into connectors/ from the
marketplace, and ci/package.sh never shipped scripts/ in the first place — so on
every installed box requirements.txt was pulling google-auth, googlemaps,
paramiko, trendspyg and friends for files that did not exist there.

requirements.txt now states what it is actually for: the two TTS plugins, which
spawn a bare `python3` on an embedded server script and so have no dependency
reconciler of their own. A connector's deps stay with the connector —
`ensure_installed` puts them in .pydeps/node_modules inside the user's
container, `ensure_installed_host` beside the files for a global one.

The venv itself stays load-bearing for those two plugins and for the host pip
that installs a global connector's deps, so the run/install/update scripts keep
creating it — but their "Python MCP servers will be unavailable" warning was
naming the one thing that no longer depends on it, and now says what really
breaks.

CONNECTOR_MANIFEST_GUIDE.md moves to the repo root: it was the one thing in
scripts/ still referenced (CLAUDE.md), and being under a gitignored directory it
had never been committed at all.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

install-nightly.sh

@@ -192,7 +192,7 @@ check_optional_deps() {
     if command -v python3 >/dev/null 2>&1; then
         info "✔ Python 3 found ($(python3 --version 2>&1 | head -1))"
     else
-        warn "Python 3 not found — Python MCP servers (Gmail, GCal, GMaps, ...) will not work."
+        warn "Python 3 not found — the TTS plugins and host-run connectors will not work."
         echo "  Install it from https://www.python.org/downloads/"
         echo ""
     fi
@@ -327,13 +327,13 @@ if [ ! -f "$VENV_DIR/bin/python3" ] || ! "$VENV_DIR/bin/python3" -m pip --versio
     if command -v uv >/dev/null 2>&1; then
         uv venv --seed "$VENV_DIR" && uv pip install -r "$REQUIREMENTS" \
             && info "✔ Python venv ready (uv)" \
-            || warn "Python venv setup failed — Python MCP servers will be unavailable."
+            || warn "Python venv setup failed — the TTS plugins and host-run connectors will be unavailable."
     elif command -v python3 >/dev/null 2>&1; then
         python3 -m venv "$VENV_DIR" && "$VENV_DIR/bin/pip" install -r "$REQUIREMENTS" \
             && info "✔ Python venv ready (pip)" \
-            || warn "Python venv setup failed — Python MCP servers will be unavailable."
+            || warn "Python venv setup failed — the TTS plugins and host-run connectors will be unavailable."
     else
-        warn "python3 not found — Python MCP servers will be unavailable."
+        warn "python3 not found — the TTS plugins and host-run connectors will be unavailable."
     fi
 else
     info "✔ Python venv already exists"