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.

interfaces/Crafter.Review-Run.cppm

@@ -199,9 +199,9 @@ export namespace Crafter::Review::Run {
         // {lens file: environment}, in the config's lens order: the dump, the
         // resume file and the scratch dir's marker write it in that order.
         Json environments = Json::object();
-        // The working directory: the config, the env file and the slots are
-        // its, the lens processes run in it, and every path logged is relative
-        // to it.
+        // The working directory: the config and the slots are its, the seats
+        // file is looked up from it (SeatPool::ResolveSeatsFile), the lens
+        // processes run in it, and every path logged is relative to it.
         std::filesystem::path repo;
         // The repository under review, from the artifact's freeze record (the
         // working directory when it has none): the prompt names it, and the
@@ -278,6 +278,8 @@ export namespace Crafter::Review::Run {
         std::unique_ptr<Memory::Sampler> sampler;
         std::unique_ptr<Pool::Runner> runner;
         Json apiCfg = Json::object();
+        // The placement settings Gate 0 laid out (SeatPool::SettingsOf).
+        std::map<std::string, std::string> settingsEnv;
         std::unique_ptr<SeatPool::Ledger> ledger;
         std::vector<Json> seats;
         std::map<std::filesystem::path, Json> envMarkers;