j139 dotenv: strip trailing inline comments and warn on non-token values

A `#` preceded by whitespace and outside quotes now ends the value, so
`TR_DEBUG_DRAW=0      # hides the grid` resolves to `0` instead of the
whole tail. Values that are still not plain tokens (whitespace, `#`, an
unclosed quote) get one `[dotenv] WARNING` line naming file, key, raw value
and the fact that the reader falls back to its DEFAULT, instead of being
applied silently. Guard test 29 -> 47 checks.

docs/env_reference.md

@@ -8,7 +8,9 @@ surprise you.
 
 1. In the bot folder, copy `.env.example` to `.env`.
 2. Open `.env` and set the knobs you want. One `KEY=VALUE` per line. Lines
-   starting with `#` are comments.
+   starting with `#` are comments. A trailing comment is allowed and stripped
+   (`KEY=0  # off`) as long as the `#` is outside quotes; a value that still
+   contains whitespace or a `#` after that gets one `[dotenv] WARNING` line.
 3. Start the bot from the bot folder (`./ModularBot`). It picks up `.env`
    automatically.
 4. To use a different file, pass it on the command line: