Remote tools: approval time limits, background commands and a host inventory

What

Remote tools let a session run tools on another machine. A feature flag is a switch that can turn behaviour on or off without a new release. Several changes arrive behind tengu_violin_* flags:

• Approval time limit: tengu_violin_corner adds a max_ask_ms limit on how long an approval request may wait.
• Stale answers: an old approval is now refused differently depending on whether it was dated ("aged allow refused") or not ("undated allow refused"). Before, only undated approvals older than a fixed window were refused.
• Full queue: when all pending approval slots are taken, a distinct message is shown, and only requests older than max_ask_ms plus some slack are pushed out. Standing approvals also record what was offered.
• Carried-over approvals: when a resumed call finds the host still waiting for approval, it can now carry that request over instead of treating it as lost. This needs max_ask_ms set, a recent call and tengu_violin_corner on.
• Approval wait: tengu_violin_spruce sets askWaitMs, how long the approval card waits, with the built-in value used when it is missing or out of range.
• Background commands: a new background_shells capability lets remote callers run background Bash commands on this machine. They stop when serving ends, and the notes say "No background commands." or "Up to ... background Bash commands". tengu_violin_varnish (fallback false) controls this support.
• Command status: a caller can ask whether a background command exited, is running or was cancelled, with its exit code. The host keeps the last 16 ended commands, and if it cannot answer the error says it "did not say what became of background command".
• Host inventory: with tengu_violin_rib, the host can report its CPU count, memory, free disk and which command-line tools (such as gcloud, aws, gh, jq) are installed.

In readings taken before this release, the flag service returned tengu_violin_corner, tengu_violin_rib and tengu_violin_varnish on for this site's account and for the anonymous baseline. Nothing has been read about tengu_violin_spruce. No reading has been taken under this release yet.

Why

A remote caller can now see more of the host machine and leave Bash commands running there, and approval requests have firmer time limits. If you serve tools to a remote session, expect it to learn your machine's resources and installed tools when that flag is on.