v2 CLI: --target as a closed choice over rostered TargetModels (Rust, C, Swift); usage refusals exit 2

[gunbai-bot]

Slice-1 prerequisite for generating the approve-ios Swift from .dag (dashboard node adhoc-1a935b07-173). The design is approved by the parent lane: emit goes through the v2 route, which is rows only, with no v1 growth.

What changes

• v2.cli.compile_cli adds CliEmitTarget = CliTargetRust | CliTargetC | CliTargetSwift. Each arm names one rostered TargetModel through cli_emit_target_model, and v2_cli_run reads its target only from the plan. Previously rust_target_model() was hardwired.
• The default is a declared plan row. cli_default_emit_target = CliTargetRust is the argv every existing caller (the instruments) already spawns.
• An unknown or dangling --target refuses at the parse with cli_unknown_target or cli_target_missing_value, and the detail names the roster. The target is never a free string.
• The exit status is split. Plan refusals are now CliUsageRefused and exit exit_code_misuse (2). Emit refusals stay exit_code_general_error (1). This is the split v2.compiler.compile native_driver_plan_exit already makes.
• The seed harness is updated to match. native_lane_runner.rs gets the declared usage line, and its no-entry control now expects exit 2.
• Claims: each spelling selects its own arm, a missing --target plans the default, unknown and dangling targets refuse, and there are exact exit codes for a usage refusal and for an emit refusal.
• New recurring-failure-mode row v2_native_route_exceeds_the_default_remote_runner_memory. It records the measured OOM receipts.

History

Swift and C were first held back because their target modules did not emit to Rust. #12270 fixed that (merged), so all three are rostered. The RFM row moved to #12268.

Evidence, stated honestly

• cargo check -p v1-compiler is green.
• The claim file has not been executed yet. A gunbc run --claim-run of src/v2/test/claim/cli/v2_native_cli_test.dag was OOM-killed (137, oom_kill 4) on the 7 GB BuildBuddy runner, the same class the new RFM row records. So the required floor on this PR is the first execution of these claims.
• Not evidenced end to end: --target c or --target swift on a real closure. The v2 closure-emit route still refuses member bodies for every target (CLI_DOOR_EMIT_BODY_REFUSAL). That capability is Gen-two #4: the door renders a module and its members' bodies through Rust's rows; a module reaching type projection refuses #12239, and the Swift protocol slice is stacked on it.

🤖 Generated with Claude Code

[briansrls]

APPROVE-MERGE at exact head 12c70113f3d39a6d7e438b876a57a2ad8b243409.

The target selection is correctly modeled as plan data rather than a free emitter string. CliEmitTarget is closed over Rust/C/Swift; each arm has an exhaustive spelling projection and TargetModel projection; cli_default_emit_target records the existing caller behavior as Rust; and v2_cli_run consumes only the target carried by the parsed plan. An unknown or dangling --target therefore refuses before source walking or emission.

The exit split is also correctly placed. Parse/plan failures become CliUsageRefused and map to GNU misuse status 2, while an admitted plan whose ingest or emission refuses remains CliRunRefused and maps to general error status 1. The seed door's no-entry control and usage string move with that contract; direct plan constructors are updated explicitly rather than relying on a hidden default.

The claims discriminate all three spellings, the no-option default, unknown and dangling target forms, and the exact 2-versus-1 statuses. Their execution on the required floor closes the PR body's earlier local OOM gap. emit-build additionally establishes that the native CLI door still emits and builds with the C and Swift target modules in its closure after #12270.

The scope boundary is honest: this lands target planning and routing, not successful member-body emission for a real C or Swift closure. That remains gated on #12239 and is not treated here as executing end-to-end evidence.

Run 36110505850 passes compiler, clippy, emit-build, floor and witnesses at this exact SHA. GitHub reports CLEAN and mergeable.

No source condition remains unless the head moves. The merge queue remains authoritative for the composed revision.