feat(seats): the env file's settings count, and a machine's own seats file

ApiConfig and PoolConfig read the seat order, the budgets and the
concurrency from the process environment alone, so a `.env` that said
REVIEW_GATES_SEAT_ORDER=oauth-first ordered nothing: the Python driver
reads those lines from the file under the process environment
(config_env, 2026-10-17: a setting lives beside the seats it orders).
SeatPool::SettingsOf does the same - the file's placement settings
under the process environment, in a map handed to the placement readers
alone (ApiConfig, PoolConfig, Seats::ConfigFromEnv) - and leaves the
process environment untouched, so no other reader sees a line of the
file: a path's or a binary's line reaches nothing, and two drivers
reading one .env keep one board and one ledger. The placement settings
are one list, SeatPool::PlacementSettings - the fifteen names those
readers read - for the map, the run's log and what makes a working
directory's .env a seats file; a REVIEW_GATES_* line of any other name
stays out of the map and is named, by the run's log and on `seats`'s
stderr. One dotenv grammar serves the tokens and the settings
(Seats::DotenvLines).

`run` and `seats` resolve the file from their own --env-file
(SeatPool::ResolveSeatsFile): the --env-file, else $SEATS_ENV_FILE, else
the working directory's .env - the operator's, as the Python driver and
`seats` read it, not the repository under review's - when it is a file
holding a seat or a placement setting, each with a value, or one that
cannot be read as UTF-8 text (its error is then the command's) - a
readable application .env, its Vite or Supabase lines, one of blank
placeholder lines or one that is no file is passed over, and the run
says so - else the machine's own
$XDG_CONFIG_HOME/crafter-review/env, else ~/.config/crafter-review/env:
one file for every repository on a machine, a repository's seats .env
winning over it. Each file is read once and the settings and the tokens
are taken from that read (SeatsFile::Text), so a file that can be read
only once - a pipe, `--env-file <(gpg -d seats.env.gpg)`, a FIFO - gives
its settings and its seats alike, and a failed read raises its own error
where the tokens are laid over the environment: SeatPool::WithFileTokens,
for `run` and `seats` alike, and LoadSeats takes the merged environment
and no longer reads a file by path. An empty `seats --env-file` means no file
now, as it did for `run`, and the `seats` report names the side that
runs first (it said "api seats run first" whatever the order).

Runs, Commands and KernelModes, the tests that run `run` and `seats`,
point XDG_CONFIG_HOME, and HOST_XDG_CONFIG_HOME for the Flatpak, at a
path of their own that nothing creates, so a global file stays out of
them; the grammar, the settings and their precedence, the lookup and the
one read have their tests, a run with `--env` (a prefix) and with a
repeated --env-file, and a `seats` with `--env`, take tokens and
settings from the one file, an application's .env and a venv are passed
over, a FIFO is read once, no line of the file reaches `stop`, every
listed placement setting moves a reader, another REVIEW_GATES_* line is
named and a .env of blank lines passed over, and the
README, the environment table and the procedure say the new rule.

tests/OpenCode/main.cpp

@@ -60,15 +60,18 @@ namespace {
 
         const fs::path envFile = td / ".env";
         Write(envFile, "CLAUDE_CODE_OAUTH_TOKEN1=tok\nOPENROUTER_KEY=sk-or-one\n");
+        // The seats file as run and seats take it: one read, its tokens over
+        // an environment (an empty one here).
+        const std::map<std::string, std::string> fileEnv = SeatPool::WithFileTokens({}, SeatPool::ResolveSeatsFile(envFile.string(), td));
         auto ids = [](const std::vector<Json>& seats) {
             std::vector<std::string> out;
             for (const Json& s : seats) out.push_back(s.at("id").get<std::string>());
             return out;
         };
         Check("OPENROUTER_KEY is a seat only on request",
-              ids(SeatPool::LoadSeats({}, envFile, "")) == std::vector<std::string>{"1"} && ids(SeatPool::LoadSeats({}, envFile, "openrouter")) == std::vector<std::string>{"or1"});
+              ids(SeatPool::LoadSeats(fileEnv, "")) == std::vector<std::string>{"1"} && ids(SeatPool::LoadSeats(fileEnv, "openrouter")) == std::vector<std::string>{"or1"});
         try {
-            SeatPool::LoadSeats({}, envFile, "or1,1");
+            SeatPool::LoadSeats(fileEnv, "or1,1");
             Check("an OpenRouter seat never shares a pool with Anthropic seats", false);
         } catch (const std::invalid_argument& e) {
             Check("an OpenRouter seat never shares a pool with Anthropic seats", std::string_view(e.what()).contains("cannot share"), e.what());