Let CLI flags bootstrap config without a file or env

[glslang]

Problem

load_config errored on a missing AGENT_NOTIFY_TOKEN before main() applied the --token/--server CLI flags. So when there was no bridge.toml and no env var, passing the flags alone could not start the bridge:

$ agent-notify-bridge --server http://host:8787 --token secret
Error: set AGENT_NOTIFY_TOKEN or create bridge.toml at one of: ...

The flags were applied only after the load already failed.

Fix

Defer the requirement check until the config layers are merged:

• load_config returns an empty token instead of erroring when AGENT_NOTIFY_TOKEN is unset, so CLI flags can still supply it.
• BridgeConfig::token is now #[serde(default)], so a bridge.toml may set server_url and leave the token to --token/the env var.
• New settings::validate() checks the fully-merged config (file/env + CLI overrides) and is called from main() after the overrides are applied. A token from any layer now satisfies the requirement, and the error message lists all three sources.

Precedence is unchanged: CLI flags override the file/env base.

Tests

New unit tests in settings.rs:

• validate accepts a complete config and rejects a blank token / blank server (with the expected messages).
• cli_token_bootstraps_base_without_token — mirrors main(): an empty-token base (as from the env path with no AGENT_NOTIFY_TOKEN) fails, then validates once a --token override is applied.
• read_config parses a file that omits the token (defaulted) and a fully-populated file.

cargo fmt --check, workspace clippy -D warnings, and cargo test all pass.

End-to-end: with no bridge.toml and no env vars, agent-notify-bridge --server ... --token ... --mock-display now boots into the tray + worker connect loop instead of erroring on a missing token.

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

❌ Patch coverage is 82.92683% with 21 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.25%. Comparing base (f1e0685) to head (5078aa8).

Files with missing lines	Patch %	Lines
crates/agent-notify-bridge/src/settings.rs	83.60%	20 Missing ⚠️
crates/agent-notify-bridge/src/main.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #23      +/-   ##
==========================================
+ Coverage   52.10%   58.25%   +6.14%     
==========================================
  Files           8        8              
  Lines        1023     1121      +98     
==========================================
+ Hits          533      653     +120     
+ Misses        490      468      -22     

Flag	Coverage Δ
rust	58.25% <82.92%> (+6.14%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
crates/agent-notify-bridge/src/main.rs	0.00% <0.00%> (ø)
crates/agent-notify-bridge/src/settings.rs	84.50% <83.60%> (+84.50%)	⬆️

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[glslang]

@cursor review

[cursor]

PR Summary

Low Risk
Local bridge client configuration and startup ordering only; no server auth or network protocol changes.

Overview
Fixes agent-notify-bridge startup when credentials come only from --server / --token (or env) without a full bridge.toml. Required checks move from load_config to a new validate in main after CLI overrides, so flags are no longer ignored by an early missing-token error.

load_config now builds config as environment base + per-field file overlay (blank/omitted file fields keep env values), instead of treating a partial file as the whole config. token in TOML is optional via #[serde(default)]; read_config no longer rejects empty tokens at parse time.

Unit tests cover validate, CLI token bootstrap, overlay precedence, and parsing files with or without a token.

^{Reviewed by Cursor Bugbot for commit 5078aa8. Configure here.}

[cursor]

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^{Reviewed by Cursor Bugbot for commit 5078aa8. Configure here.}