[plan-08] OpenCode Integration Event-Contract Correctness — make the OpenCode plugin actually capture

Defect

claude-mem's OpenCode plugin was written against event names that do not exist in OpenCode's hook API (e.g. session.created, message.updated, session.compacted, file.edited, session.deleted). Because no real event ever fires, sessions are never initialized and no observations are captured — while claude-mem install still reports success. The result is a silent dead loop: OpenCode users believe memory is recording and it is recording nothing. A second defect compounds it: the OpenCode search client parses data.items while the worker returns Claude-style data.content blocks, so even manual search returns "No results", and it resolves the worker port from the wrong source.

The architectural fix is to bind the plugin to OpenCode's real event contract and to the worker's actual response shape, then add a contract test so a future OpenCode API change fails CI rather than silently disabling capture.

Children

• #2435 — plugin subscribes to non-existent OpenCode event names → zero sessions/observations recorded
• #2406 — claude_mem_search always returns "No results" (data.items vs data.content); worker-port resolution uses the wrong source
• #2419 — feature framing of the same gap: OpenCode plugin lacks tool.execute.after observation capture
• #2462 — duplicate user report: OpenCode install reports success but captures no memory

Fix sequence

1. Rebind to real events: rewrite the plugin against OpenCode's actual hooks (tool.execute.after, chat.message, experimental.session.compacting, …); add session init + observation POST on the correct events (#2435, #2419).
2. Fix the search client: parse the worker's data.content block shape; resolve the worker port from the authoritative settings source, with the env override honored (#2406).
3. Contract test: a test that asserts the plugin subscribes only to event names OpenCode actually emits, and that the search client parses the worker's real response shape. This is the regression guard.
4. Install honesty: OpenCode install must verify capture is live (one round-trip) before reporting success, so a future contract break surfaces at install time (ties to plan-04).

Test matrix

Surface	Input	Required behavior
Tool execution in OpenCode	a tool call	tool.execute.after fires → observation POSTed → row appears
Session lifecycle	open/compact/close	session init + compaction handled via real events
claude_mem_search	a query with known results	parses data.content; returns the rows (not "No results")
Worker-port resolution	non-default port via env/settings	client targets the correct port

The matrix lives in CI. An OpenCode-capture regression must fail CI before a user can file.

Out of scope

• Claude Code hook IO discipline → plan-01.
• Worker write-path / persistence correctness → plan-09.
• The worker's own search SQL source-scoping → plan-09.