ci.yml resolves an unpinned nightly with -D warnings, breaking cargo clippy on every branch since 22 Aug

[decrypto21]

Summary

.github/workflows/ci.yml resolves the Rust toolchain at run time:

- uses: dtolnay/rust-toolchain@5b842231ba77f5c045dba54ac5560fed2db780e2 # nightly
  with:
    toolchain: nightly

and runs clippy with -D warnings, so any lint a future nightly introduces fails the workspace with no change in the repository. A recent nightly added recursion_depth_exceeding_limit, and truapi-server trips it:

error: overflow evaluating the requirement
  --> rust/crates/truapi-server/src/runtime/pairing_host.rs:2423:5
   = help: consider increasing the recursion limit by adding a
           `#![recursion_limit = "256"]` attribute to your crate (`truapi_server`)
   = note: `-D recursion-depth-exceeding-limit` implied by `-D warnings`
   = warning: this was previously accepted by the compiler but is being phased out

Proving request_login's boxed trait future Send recurses through SsoPairingFlow::request_session and exceeds the default 128-step budget. The chain is not recursive, only deeper than the default allowance; the compiler previously accepted the give-up silently.

Every CI run repo-wide since 22 Aug has failed. There are three:

run	branch	result
2026-08-22 11:13	rfc/spa-worker-calls (#468)	failure
2026-08-24 07:26	nidish/debug-host-port (#295)	failure
2026-08-24 07:33	nidish/debugger-rfc (#315)	failure

Other open PRs show a green Rust workspace from runs between 04 and 21 Aug, predating the lint; they turn red on their next run. main last ran 21 Aug. #315 is the control: its entire diff is one markdown file and it fails identically, so main is affected.

Fix

#![recursion_limit = "256"] in truapi-server, as the diagnostic suggests.

Options — toolchain pinning

The lint is the symptom; the unpinned toolchain is why it lands as a failure rather than an upgrade. There is no rust-toolchain.toml today.

• Add a dated rust-toolchain.toml, so nightly moves only when the pin is bumped.
• Or pin toolchain: in ci.yml to a dated nightly.
• Or keep nightly floating and drop -D warnings for the nightly job, reporting new lints without failing the build.

[decrypto21]

Closed because of #475.