Suppress default team note when the team is project configuration

[schpetbot]

issue query prints Note: using default team ... whenever the team scope falls back to the configured default. The note exists to flag ambient defaults (a global config file or a shell-exported LINEAR_TEAM_ID) silently narrowing a query — but it also fired when the team came from the project's own linear.toml or .env, i.e. explicit, directory-scoped configuration where the reminder is just noise on every query.

What changed

• src/config.ts keeps global and project config separate (instead of spread-merging) and records which env keys were actually applied from a project .env, exposing a typed getOptionWithSource() that reports where each option was resolved from: cli, env, project-env, project-config, or global-config. getOption() keeps its interface and delegates — this also removed its two as casts.
• src/utils/linear.ts adds getTeamKeyWithSource(); getTeamKey() delegates so all other call sites are untouched.
• issue query gates the note through an exhaustive shouldShowDefaultTeamNote(source) switch: suppressed for project-scoped sources, kept for ambient ones.

Effective team_id source	Note?
--team / --all-teams	n/a (bypasses the default branch)
project linear.toml / .linear.toml (cwd or git root)	suppressed
project .env	suppressed
global config (XDG / ~/.config / APPDATA)	shown
shell-exported LINEAR_TEAM_ID	shown

Tests

• Subprocess provenance tests for every source category, run with clearEnv so a runner-supplied LINEAR_TEAM_ID can't leak into module-init config loading.
• A regression test that a present-but-invalid project value still shadows a valid global value (preserving the old spread-merge behavior).
• In-process integration tests for both note outcomes, plus a full policy-matrix table test of the exported helper.