feat: context parity across cloud vendors + cloud env configs (ARN-415)

[rita-aga]

Distillation only delivered the global layer to Claude (a .claude/ hook). Cursor and Codex cloud agents read the repo AGENTS.md and never saw the global rules. This vendors the stack global into AGENTS.md (one path all three harnesses read, single source stays arni-labs/stack via stack/vendor-global.sh), removes the redundant Claude-only hook, and adds cloud-setup.sh + .cursor/environment.json so a cloud agent's machine installs the shared stack skills.

Authored by Fable 5 via Claude Code.

Greptile Summary

This PR moves shared global agent guidance into the repository-wide AGENTS.md, removes the Claude-only injection hook, and adds cloud environment bootstrapping for shared stack skills and repository dependencies.

• Vendors the shared stack instruction layer into AGENTS.md.
• Removes .claude/global.md and its SessionStart hook.
• Adds Cursor snapshot configuration and a stack synchronization script.

Confidence Score: 4/5

The setup failure masking should be fixed before merging because it can accept an incomplete cloud environment and defer failures until agent work begins.

The new Cursor installation command and cloud bootstrap suppress failures from required dependency and skill installation, so snapshot creation cannot distinguish a usable environment from a partially configured one.

Files Needing Attention: .cursor/environment.json and scripts/cloud-setup.sh

Important Files Changed

Filename	Overview
.cursor/environment.json	Adds the Cursor snapshot installer, but suppresses setup diagnostics and converts every bootstrap failure into success.
scripts/cloud-setup.sh	Clones and synchronizes shared stack skills, while ignoring update and synchronization failures and unconditionally reporting installation.
AGENTS.md	Vendors the shared global instruction layer ahead of the existing repository-specific contract.
.claude/settings.json	Removes the obsolete SessionStart context hook while retaining the stack plugin configuration.
.claude/global.md	Deletes the former Claude-specific copy of global instructions.
.claude/hooks/global-context.sh	Deletes the hook that conditionally emitted the former Claude-specific global instruction file.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
    Snapshot[Cursor snapshot build] --> Install[environment.json install]
    Install --> Stack[cloud-setup.sh]
    Stack --> Clone[Clone or update stack]
    Clone --> Sync[Run stack sync.sh]
    Sync --> Repo[make setup]
    Repo --> Ready[Configured cloud environment]
    Stack -. masked failure .-> Incomplete[Incomplete environment accepted]
    Repo -. masked failure .-> Incomplete

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Greptile also left 1 inline comment on this PR.

[greptile-apps]

Setup failures are masked

When stack synchronization or repository setup fails, the trailing || true accepts the snapshot while 2>/dev/null discards its diagnostics, causing the cloud agent to start without required skills, dependencies, WASM targets, fetched crates, or environment configuration.