fix(claude): symlink CLAUDE.md → AGENTS.md so Claude-model sessions inherit DM context

[chubes4]

Closes #108

Problem

upgrade.sh Phase 5 regenerates AGENTS.md via wp datamachine memory compose, but CLAUDE.md is only generated by hooks/dm-agent-sync.sh which is gated to Claude Code's SessionStart hook. On opencode-runtime + kimaki-bridge installs, CLAUDE.md is never created.

Empirical evidence

On the extrachill.com VPS, a fresh OpenCode session running claude-opus-4-7 does not honor SOUL.md/MEMORY.md content and self-reports the DM bundle as "not in context." A side-by-side fresh session with the same config running glm-5.1 self-identifies as "Extra Chill Bot" with phrasing pulled directly from SOUL.md.

AGENTS.md alone is insufficient for the Claude model — CLAUDE.md is needed.

Why a symlink (Option 3)

Three options were considered in #108:

1. Duplicate compose — run datamachine memory compose CLAUDE.md alongside AGENTS.md. Risks drift if one compose succeeds and the other fails, plus duplicated bytes on disk.
2. Refactor the hook — pull dm-agent-sync.sh out of the Claude Code SessionStart gate and run it for opencode too. Larger blast radius, requires reworking the runtime hook contract.
3. Symlink CLAUDE.md → AGENTS.md ✅ — self-healing on regeneration, no duplication, no drift, minimal change. OpenCode reads both filenames; Claude Code reads CLAUDE.md.

OpenCode source globs ["AGENTS.md", "CLAUDE.md", "CONTEXT.md"] upward from cwd (deduped), so writing CLAUDE.md is purely additive — it does not break opencode users and gives Claude-model users the context they need.

Changes

upgrade.sh Phase 5

After wp datamachine memory compose AGENTS.md succeeds, ensure CLAUDE.md → AGENTS.md symlink exists. Dry-run path prints the would-be action. Skips when CLAUDE.md is a regular file (claude-code/studio-code runtimes ship their own template-based CLAUDE.md).

runtimes/opencode.sh::runtime_generate_instructions

Fresh installs via the opencode runtime now also create the symlink — both on the compose-success path and on the static-template fallback path. Extracted into helper _opencode_symlink_claude_md so it is called from every code path that writes AGENTS.md, including the "AGENTS.md already exists, skipping" branch (so existing installs get the symlink on next run even without a regeneration).

Scope

• ✅ Tied to AGENTS.md regeneration, runs under --agents-md-only (verified via dry-run, see below)
• ✅ Relative target (ln -sf AGENTS.md CLAUDE.md from $SITE_PATH) — survives directory moves
• ✅ No CHANGELOG.md or VERSION edits (homeboy owns both)
• ✅ Idempotent — ln -sf overwrites an existing symlink, helper guards against clobbering a real CLAUDE.md file

Verification

./upgrade.sh --dry-run --agents-md-only on extrachill.com:

[wp-coding-agents] Phase 5: Regenerating AGENTS.md...
[dry-run] Would backup /var/www/extrachill.com/AGENTS.md → ...AGENTS.md.backup.20260503-182449
[dry-run] Would run: wp datamachine memory compose AGENTS.md --allow-root
[dry-run] Would symlink /var/www/extrachill.com/CLAUDE.md → AGENTS.md (Claude-model context)

bash -n syntax check passes on both modified files.

git diff origin/main shows ONLY the symlink addition + dry-run handling. No unrelated edits.

Acceptance criteria (from #108)

• On opencode-runtime + kimaki-bridge installs, CLAUDE.md exists after upgrade.sh runs
• CLAUDE.md content is identical to AGENTS.md (it is the same file via symlink)
• Symlink is regenerated/preserved on subsequent upgrade.sh runs (idempotent)
• Symlink uses a relative target so directory moves don't break it
• Fresh installs via the opencode runtime also get the symlink
• claude-code / studio-code runtimes that ship a real CLAUDE.md are not clobbered
• --agents-md-only scope flag covers the symlink (it is part of Phase 5, not gated separately)
• No changes to CHANGELOG.md or VERSION