fix(opencode): route session.created through event dispatcher (421)

[ousamabenyounes]

Summary

Fixes #421 — opencode plugin's session.created handler never fires on opencode >= 1.15.

opencode >= 1.15 dispatches session/lifecycle events through a single event handler that switches on event.type (plugin docs). The previous direct top-level 'session.created' key was silently ignored, so the .caveman-active flag was never written on session start and the per-prompt reinforcement in tui.prompt.append bailed every turn (it reads the flag and returns when empty). Always-on caveman in opencode kept working only via the separately-installed ~/.config/opencode/AGENTS.md; the plugin's dynamic-state layer was silently inert.

tui.prompt.append is unchanged — TUI events still use the direct-key pattern.

Fix

• Extract handleSessionCreated (single source for session-start logic, reusable from any dispatcher).
• Replace the direct 'session.created' key with an event handler that filters on event.type === 'session.created'.

TDD verification

• RED check (tests on main without prod fix): 2/2 new tests fail
  • event handler missing — typeof handlers.event === 'function' asserts undefined
  • handlers.event is not a function — TypeError on the new event-dispatch test
• GREEN check (tests with prod fix): 2/2 new tests pass

Verification

• Baseline tests on main: 51 total, 47 pass, 4 pre-existing failures (installer command-file copy, unrelated)
• Post-fix tests: 52 total, 48 pass, same 4 pre-existing failures (no green→non-green flips, no new failures)
• New tests: 1 added (event dispatcher ignores unrelated event types + dispatches session.created); 1 modified to use the v1.15 dispatch shape and assert the direct-key is gone

Files changed

File	Change
src/plugins/opencode/plugin.js	Extract handleSessionCreated; route through event dispatcher
tests/installer/opencode.test.mjs	Update smoke test to v1.15 API; add event dispatcher coverage test

[ousamabenyounes]

Verified RED/GREEN proof (run on eab8052 against origin/main)

Test runner: node --test --test-name-pattern='opencode event handler dispatches|opencode plugin handles /caveman ultra and stop caveman via tui.prompt.append' tests/installer/opencode.test.mjs.

Procedure:

1. GREEN — fix as committed (HEAD = eab8052)
2. git checkout origin/main -- src/plugins/opencode/plugin.js (revert prod fix, keep new tests)
3. RED — same command, captured below
4. git checkout HEAD -- src/plugins/opencode/plugin.js (restore)

GREEN (with fix)

# Subtest: opencode plugin handles /caveman ultra and stop caveman via tui.prompt.append
ok 1 - opencode plugin handles /caveman ultra and stop caveman via tui.prompt.append
  ---
  duration_ms: 92.969133
  type: 'test'
  ...
# Subtest: opencode event handler dispatches session.created and ignores other event types
ok 2 - opencode event handler dispatches session.created and ignores other event types
  ---
  duration_ms: 106.131722
  type: 'test'
  ...
1..2
# tests 2
# suites 0
# pass 2
# fail 0
# cancelled 0
# skipped 0
# todo 0
# duration_ms 268.942668
# pass 2
# fail 0

RED (prod fix reverted, tests unchanged)

# Subtest: opencode plugin handles /caveman ultra and stop caveman via tui.prompt.append
not ok 1 - opencode plugin handles /caveman ultra and stop caveman via tui.prompt.append
  ---
  duration_ms: 103.986678
  type: 'test'
  location: '/tmp/contribute-caveman-421/tests/installer/opencode.test.mjs:251:1'
  failureType: 'testCodeFailure'
  error: |-
    event handler missing
    + actual - expected
    
    + 'undefined'
    - 'function'
    
  code: 'ERR_ASSERTION'
  name: 'AssertionError'
  expected: 'function'
  actual: 'undefined'
  operator: 'strictEqual'
  stack: |-
    TestContext.<anonymous> (file:///tmp/contribute-caveman-421/tests/installer/opencode.test.mjs:281:12)
    async Test.run (node:internal/test_runner/test:1054:7)
    async startSubtestAfterBootstrap (node:internal/test_runner/harness:296:3)
  ...
# Subtest: opencode event handler dispatches session.created and ignores other event types
not ok 2 - opencode event handler dispatches session.created and ignores other event types
  ---
  duration_ms: 120.196507
  type: 'test'
  location: '/tmp/contribute-caveman-421/tests/installer/opencode.test.mjs:292:1'
  failureType: 'testCodeFailure'
  error: 'handlers.event is not a function'
  code: 'ERR_TEST_FAILURE'
  name: 'TypeError'
  stack: |-
    TestContext.<anonymous> (file:///tmp/contribute-caveman-421/tests/installer/opencode.test.mjs:309:20)
    async Test.run (node:internal/test_runner/test:1054:7)
    async Test.processPendingSubtests (node:internal/test_runner/test:744:7)
  ...
1..2
# tests 2
# suites 0
# pass 0
# fail 2
# cancelled 0
# skipped 0
# todo 0
# duration_ms 306.54369
# pass 0
# fail 2

Both tests fail with the exact assertion messages the test bodies expect (event handler missing and handlers.event is not a function), proving the tests catch the bug rather than asserting internal implementation.

Full captured logs persisted locally and available on request.