integration: batch-merge V1 PRs #12 #13 #14 #15 #16 (conflicts resolved)

[ranxianglei]

What

Batch integration of the five open 5258MF V1 PRs onto current master, with their two inter-PR conflicts pre-resolved so the whole set lands in one mergeable unit.

Includes (merge order used):

1. fix: align system prompt with PI rules #14 — align system prompt with PI rules
2. test: repair root smoke harness #16 — repair root smoke harness
3. fix(v1): normalize ref tag placement #12 — normalize V1 ref tag placement
4. feat(v1): prefer reported usage for nudge calculations #15 — prefer reported usage for nudge
5. fix(v1): preserve truncated tool result bodies #13 — preserve truncated V1 tool result bodies (both conflicts surface here)

Conflicts resolved

• packages/billion-context-opencode/src/messages-v1.ts (fix(v1): preserve truncated tool result bodies #13 vs feat(v1): prefer reported usage for nudge calculations #15): kept the richer state.metadata type ({ interrupted?: boolean; output?: unknown; [key: string]: unknown }); fix(v1): preserve truncated tool result bodies #13's applyToolBody reads metadata.interrupted/metadata.output against it cleanly.
• packages/billion-context-opencode/tests/messages.test.ts (fix(v1): normalize ref tag placement #12 vs fix(v1): preserve truncated tool result bodies #13): both test sets are independent additions at the same anchor → kept the union (4 tests from fix(v1): normalize ref tag placement #12 + 4 tests from fix(v1): preserve truncated tool result bodies #13).
• Post-merge fixup: removed a duplicate trimEnd helper (both fix(v1): normalize ref tag placement #12 and fix(v1): preserve truncated tool result bodies #13 independently added the identical one-line helper).

Verification (on this branch)

• npm run typecheck — pass (both workspaces)
• npm test — 50/50 pass
• npm run build — pass (676 KB bundle)
• node smoke.mjs — ALL TESTS PASSED

Scope / notes

• Touches only V1 adapter + @bili/core + smoke/devlog. Does not touch V2 (packages/v2 / v2) — V2 PRs Add OpenCode V2 adapter (v2/) on acp-kernel #4 and fix(v2): register tools with the opencode2 API shape #8 are orthogonal and remain open/blocked.
• After this merges, the five original PRs (fix(v1): normalize ref tag placement #12-test: repair root smoke harness #16) can be closed as superseded (their commits are contained here).
• Open known issue carried from fix: align system prompt with PI rules #14: kernel uses generic tool name compress in its rules while the plugin registers bili_compress — left unchanged; to be addressed separately.

[ranxianglei]

Closing as superseded. This was a batch-integration branch for the five 5258MF V1 PRs (#12–#16) with their inter-PR conflicts pre-resolved. The maintainer instead merged #12/#14/#15/#16 individually, and #13's conflicts were resolved directly on its own branch (all five are now in master), so this integration branch is no longer needed.