feat(headless): typed --console option resolution + command-line flag

Adds the first piece of the interactive headless console (docs/plans/
2026-09-07-headless-console.md): HeadlessConsoleOptions.Resolve picks
--console, then ACDREAM_HEADLESS_CONSOLE=1, then a terminal-shaped
default, matching the project's typed-options-object convention rather
than a scattered env-var read. HeadlessCommandLine.Parse now accepts
--console as a bare flag (no value token) alongside the existing
paired options. Both new launch-options.md rows are added in this
commit per LaunchOptionsDocumentationTests' bidirectional rule.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

docs/launch-options.md

@@ -93,6 +93,7 @@ dotnet run --project src\AcDream.App\AcDream.App.csproj --no-build -c Release
 | `ACDREAM_DAT_DIR` | `=<path>` | Fallback dat-directory when no positional argument is given. App: single read at `Program.cs:58`. Cli: read independently per-subcommand (each subcommand does `args.ElementAtOrDefault(N) ?? Env.GetEnvironmentVariable("ACDREAM_DAT_DIR")`) plus once more for the default (no-subcommand) asset-inventory mode at line 152. | Two of the four `Program.cs` line numbers in the raw grep (91, 135) are **not reads** — they're the literal string `ACDREAM_DAT_DIR` inside `Log.Error` usage-text messages, not `GetEnvironmentVariable` calls. Only line 58 is a real read in `AcDream.App`. | none — hard usage error (exit 2) if unset and no positional arg | `Program.cs:58` (App); `Cli/Program.cs:24,35,47,59,71,84,113,125,137,152` (every Cli subcommand) |
 | `ACDREAM_DISPLAY_PROTOCOL` | `="auto"` / `"x11"` / `"wayland"` (case-insensitive, trimmed); any other value throws `InvalidOperationException` at startup | Linux-only: forces the GLFW 3.4 platform-init hint (X11 vs Wayland vs auto) before any window is created; ignored entirely on Windows (always `Windows` protocol) | An invalid value is fatal at startup (throws before any window exists), not a silent fallback | unset → auto-detected from `XDG_SESSION_TYPE`/`WAYLAND_DISPLAY`/`DISPLAY`, falling back to GLFW `Automatic` | `GraphicalWindowBackendSelection.Resolve` (`GraphicalWindowBackendSelection.cs:26-58`) |
 | `ACDREAM_FAR_RADIUS` | `=<int>` | Overrides preset's `FarRadius` (outer streaming/reveal window, landblocks) | Enlarging changes streaming memory budget and what's resident/rendered — CLAUDE.md: leave unset for measurement/gate runs (same family as legacy `ACDREAM_STREAM_RADIUS`) | preset's `FarRadius` (Low=5, Medium=8, High=12, Ultra=15) | `QualitySettings.WithEnvOverrides` (`QualityPreset.cs:47`) |
+| `ACDREAM_HEADLESS_CONSOLE` | `=1` enables | Turns on the headless host's interactive console (docs/plans/2026-09-07-headless-console.md): a background thread reads stdin lines, each drained on the session tick through the SAME plugin-verb/client-slash-command pipeline the graphical chat box uses, with chat/lifecycle/portal output rendered to stdout. Only takes effect for `run` with a single configured session — the launcher's multi-session mode is unaffected. | Starts a background stdin-reader thread and writes plain-text lines to the same stdout stream `HeadlessDiagnosticWriter` already uses for its JSON lines — the two interleave. Only applies to `run`; `--console` (bare flag, no value) always wins over this variable, which in turn always wins over the terminal-shaped default. | unset → on when stdin is a real console, off when redirected (`!Console.IsInputRedirected`, checked once in `Program.cs`) | `HeadlessConsoleOptions.Resolve` (`Configuration/HeadlessConsoleOptions.cs`) → `HeadlessEntryPoint.Run` → `HeadlessProcessHost`'s `consoleEnabled` |
 | `ACDREAM_LIVE` | `=1` (exactly the literal string `"1"`) | Core switch: connect to a live ACE server instead of running offline/no-connect. | The 4 non-`RuntimeOptions.cs` line numbers in the raw grep are **all comments or log-message text**, not reads — `SessionStartComposition.cs:39` is inside the string `"live: ACDREAM_LIVE set but TEST_USER/TEST_PASS missing; skipping"`; `Program.cs:126` is inside a `--session-config` override log line; `GameWindow.cs:614,627` are doc comments. The only actual parse is `RuntimeOptions.cs:141`. Requires `ACDREAM_TEST_USER`/`ACDREAM_TEST_PASS` too (`HasLiveCredentials`) or the session silently reports `MissingCredentials` and skips. Forced to effectively-on (LiveMode=true) unconditionally by `--session-config` launches regardless of this var. | `false` | `RuntimeOptions.LiveMode` → `SessionStartComposition.cs` (log text only), `Program.cs:126` (log text only), `GameWindow.cs:614,627` (comments only), consumed for real via `RuntimeOptions.HasLiveCredentials` and `WorldSession`/`GameRuntime` session-start gating |
 | `ACDREAM_MAX_COMPLETIONS_PER_FRAME` | `=<int>` | Overrides preset's per-frame streaming-completion throughput cap | Directly changes the streaming admission budget measured by perf/completion gates — do not vary during a measurement run | preset's value (Low=2, Medium=3, High=4, Ultra=6) | `QualitySettings.WithEnvOverrides` (`QualityPreset.cs:59`) |
 | `ACDREAM_MSAA_SAMPLES` | `=<int>` (0/2/4/8) | Overrides preset's MSAA sample count | Changes GPU multisample anti-aliasing (visual + GPU-cost change) | preset's `MsaaSamples` (Low=0, Medium=2, High/Ultra=4) | `QualitySettings.WithEnvOverrides` (`QualityPreset.cs:48`) |
@@ -143,6 +144,7 @@ config without connecting; `run` connects.
 | `--config <path>` | The versioned headless session-configuration document. Required. | — |
 | `--config-dir` / `--data-dir` / `--cache-dir` `<path>` | Override each portable path root. | Merged over the config document's own `process.paths`; the command line wins. |
 | `-user` / `--user`, `-password` / `--password` | Direct single-session credentials, bypassing the config's credential source. | Plaintext in the process command line — prefer the config's credential reference. |
+| `--console` | Forces the interactive console on for `run` (bare flag, no value) — see `ACDREAM_HEADLESS_CONSOLE`. | Same side effects as the environment variable; this flag always wins over it. |
 | `--help` / `-h` (or no args) | Prints usage, exits 0. | — |
 
 ### `AcDream.Launcher`