fix(opencode): adopt upstream #3617 resume robustness onto fork base

[patroza]

Adopts the OpenCode session-resume hardening from upstream pingdotgg/t3code#3617 (fixes the pingdotgg#3604 class of silent context loss) onto this fork's adapter.

Why hand-ported, not cherry-picked

This fork runs ahead of upstream on @opencode-ai/sdk (1.17 vs the PR's 1.3) and passes a per-call directory to every client.session.* call, and it already had an independent, strict resume implementation. The upstream diff does not apply cleanly, so the PR's robustness was ported onto the fork's directory-aware base instead.

What changed (OpenCodeAdapter.ts)

• Schema-versioned cursor — OPENCODE_RESUME_VERSION / parseOpenCodeResume; malformed or foreign cursors are ignored (treated as "no resume") instead of throwing.
• Robust not-found — isOpenCodeNotFound classifies only structured 404 / NotFoundError signals. A confirmed miss falls back to session.create; transport / auth / 5xx errors propagate rather than masquerading as a brand-new empty session.
• Fork on cwd change — when the stored directory differs (e.g. thread moved into a git worktree), session.fork carries history into the requested directory instead of dropping context.
• Permissions on resume — session.update re-applies the current runtimeMode ruleset on reuse/fork.
• Race cleanup aborts only a session this call created; sendTurn echoes resumeCursor so ProviderService keeps the persisted cursor fresh every turn.
• Preserves the fork's per-call directory and isOpenCodeMessageAborted.

Tests (OpenCodeAdapter.test.ts)

Regression coverage for: resume (no create), fork-on-cwd, stale-404 fallback-to-create, transient-error propagation, malformed-cursor rejection, and direct isOpenCodeNotFound classification. The two obsolete hard-error-on-directory-mismatch tests were replaced.

Validation

• tsgo --noEmit clean
• OpenCodeAdapter.test.ts 23/23; full src/provider + src/orchestration suites 539 pass (6 pre-existing skips)
• vp check clean

🤖 Generated with Claude Code