🥈 [SR-05] railway-deployer — fleet integration via versioned git dep

[gHashTag]

Soul-name: Rail Conductor · Codename: LEAD · Priority: P2-MEDIUM · Kingdom: Network
Ring: GOLD I trios-igla-race-pipeline / SR-05
Part of: #446
Blocks: BR-OUTPUT(GOLD I)
Blocked by: SR-04 (issue 10)

Goal

Integrate the operator surface from gHashTag/trios-railway (bin/tri-railway 26 KB Rust, crates/trios-railway-audit, bin/tri-gardener, bin/seed-agent) as a versioned git dep. Reaffirm L1 (no .sh) by replacing any remaining shell helpers with Rust binaries.

Acceptance criteria

• rings/SR-05/ with I5 trinity.
• Deps: SR-00..04 + trios-railway-audit = { git = ..., rev = <pinned-sha> } + reqwest for Railway GraphQL.
• Public API: RailwayDeployer::deploy(&FleetSnapshot) -> Result<DeployReceipt, DeployErr>, audit() -> AuditReport, fleet_snapshot() -> FleetSnapshot.
• Observe-only mode by default (DEPLOYER_MODE=observe); DEPLOYER_MODE=apply requires explicit env.
• No .sh shipped; old shell helpers (if any) deleted in this PR.
• Doctor rule R-L1-ECHO-006 re-runs L1 check inside SR-05 tree.
• R7 audit triplet RAIL=<verb> @ project=<8c> service=<8c> sha=<8c> ts=<rfc3339> honoured (per trios-railway/AGENTS.md).
• Integration smoke against a Railway dev project.
• PR closes this issue, Agent: LEAD trailer.

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