feat: add OPENCODE_NO_NOTIFY env var to suppress notifications

[christophkroeppl]

Problem

When opencode is invoked programmatically from an external harness — build orchestrators, CI pipelines, automation scripts, etc. — desktop notifications are unhelpful and disruptive. No human is watching the process, so the notifications are pure noise.

Example: worktrunk (wt step commit) calls opencode run to generate commit messages. Each invocation triggers a "Ready for review" desktop notification that interrupts the user even though the process is fully automated and headless.

Solution

A single opt-in environment variable OPENCODE_NO_NOTIFY. When set to "1" or "true", the entire plugin is disabled at initialization — returning {} before any event listeners are registered. This means:

• No desktop notifications of any kind (idle, error, permission, question)
• Zero overhead — no handlers, no listeners, no deduplication timers
• Completely opt-in — existing behavior is unchanged when the env var is not set

Usage

# Suppress notifications for a single invocation
OPENCODE_NO_NOTIFY=1 opencode run "commit this change"

# Or set it in a wrapper/harness script
export OPENCODE_NO_NOTIFY=1
opencode run "$@"

[christophkroeppl]

There's a couple of open issues and PRs on OpenCode tackling plugin management but none allow for disabling a plugin for a single execution. Also this feature is easy enough to remove in the future if oc decides to impl. plugin suppression.