daemon: profile daemon wedges with "Failed to get current directory" after its spawn directory is deleted

[alleneubank]

Summary

The auto-spawned per-profile daemon inherits the client's working directory. Every request runs CwdGuard::change_to(req.cwd), which captures the daemon's own current_dir() so it can restore it afterwards. Once the spawn directory is deleted (a removed git worktree, for instance) getcwd fails and every request for that profile errors until the daemon is killed.

Repro (v1.34.1, macOS; same on Linux)

fnox.toml:

root = true

[daemon]
enabled = true

[providers.plain]
type = "plain"

[secrets]
FOO = { provider = "plain", value = "bar" }

mkdir a b && cd a
fnox get FOO                 # bar (spawns the daemon with cwd = a)
cd ../b && rm -rf ../a
fnox get FOO
# Error: fnox::config::error
#   × Configuration error: Configuration error: Failed to get current directory: No such file or directory (os error 2)
fnox --no-daemon get FOO     # bar
fnox daemon stop && fnox get FOO   # bar (fresh daemon)

Root cause

• start_background_for_context in src/daemon.rs detaches the daemon with setsid and null stdio but never sets a working directory, so the daemon keeps the client's cwd for its whole lifetime.
• CwdGuard::change_to in src/daemon.rs calls std::env::current_dir() before switching to the request cwd; with the spawn directory gone that call fails on every request.

Fix

Spawn the daemon with current_dir("/") next to the existing setsid; each request already switches to the client's cwd. A PR with that one-line change and a bats regression test is ready to open.

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[jdx]

Confirmed on current main on Linux. The daemon inherits the auto-starting client's cwd, and CwdGuard::change_to subsequently fails before it can switch to a new request cwd once that inherited directory is deleted.

I opened #795 to start background daemons from / and added a Bats regression test covering deletion of the spawn directory. The daemon test suite and lint checks pass.

AI-assisted — Tool: Codex; model: openai/gpt-5; version: unavailable.