fix(adapter): don't emit permissionDecision for non-PreToolUse events

[srnnkls]

Problem

fas eval --harness claude emits an invalid hook response for SessionEnd:

{"hookSpecificOutput":{"hookEventName":"SessionEnd","permissionDecision":"allow"}}

Claude Code rejects it with Hook JSON output validation failed — (root): Invalid input. hookSpecificOutput is a discriminated union keyed on hookEventName, and SessionEnd is not a valid variant — only PreToolUse carries a permissionDecision.

Root cause: ClaudeCode.RenderOutput treated permissionDecision as the default shape for every event outside a small contextOnlyEvents set. This also latently affected SessionStart, Notification, and PreCompact.

Fix

• permissionEvents (PreToolUse) → permissionDecision shape.
• contextEvents (UserPromptSubmit, PostToolUse, PostToolBatch, Stop, SubagentStart, SubagentStop) → additionalContext-only shape.
• Everything else (session-lifecycle, notifications, unknown) → bare {}, which is valid against the CC schema.
• Parse-error fallback: an unextractable hook_event_name now defaults to PreToolUse so the fail-open/fail-closed decision still renders under the one event that carries a permissionDecision.

Repro (before → after)

$ echo '{"hook_event_name":"SessionEnd",...}' | fas eval --harness claude
before: {"hookSpecificOutput":{"hookEventName":"SessionEnd","permissionDecision":"allow"}}   # rejected
after:  {}                                                                                    # valid

PreToolUse still decides: {"hookSpecificOutput":{"hookEventName":"PreToolUse","permissionDecision":"allow"}}.

Tests

• New: bare events (SessionEnd/SessionStart/Notification/PreCompact/empty) omit hookSpecificOutput; context events omit permissionDecision.
• Updated the HookEventName echo test (dropped SessionStart, now bare).
• Full suite green (go test ./...); gofmt/vet/build pass.

Note: the pre-existing golangci-lint findings (gocritic/prealloc in unrelated files, also present on main) are out of scope and untouched here.

[Copilot]

Pull request overview

Fixes Claude Code adapter output so it conforms to the Claude Code hook response schema: only PreToolUse responses include permissionDecision, context-injection events emit a context-only variant, and all other events emit a bare {} (no hookSpecificOutput).

Changes:

• Split hook events into permissionEvents (PreToolUse) vs contextEvents and render the correct JSON shape per category.
• Render bare {} for session-lifecycle/notification/unknown events to avoid emitting invalid discriminated-union variants.
• Default peekHookEventName to PreToolUse on parse-error fallback so fail-open/fail-closed still produces a decision response.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
internal/adapter/claudecode.go	Adjusts Claude Code hook response rendering to emit schema-valid shapes per hook event kind.
internal/adapter/claudecode_test.go	Updates/extends tests to cover bare events and context-only events, and adjusts hook-event echo expectations.
cmd/fas/main.go	Changes parse-error fallback hook-event-name extraction to default to PreToolUse when unextractable.

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