chore: adopt the AGENTS.md convention (fold CLAUDE.md into AGENTS.md)

[kw-tmueller]

Brings this repo onto the AGENTS.md convention. Refs owncloud/admin#249.

AGENTS.md    100644   renamed from agents.md
CLAUDE.md    120000   symlink -> AGENTS.md

• The spec says uppercase AGENTS.md, and that is what agent tooling looks for — a lowercase agents.md is simply not found on the case-sensitive filesystems of our Linux CI runners.
• CLAUDE.md becomes a symlink to AGENTS.md, so Claude Code reads the same content and there is no second file to keep in sync.

This one was done by hand. The org-wide sweep (scripts/sync-agents-md.py in owncloud/admin) deliberately refuses any repo whose CLAUDE.md is a real file, because replacing it with a symlink would silently discard its content. Here that content has been folded into AGENTS.md first, so nothing is lost:

• Added a Test Architecture section: the World/PicoContainer layer model and the per-directory responsibilities (steps, preconditions, tasks, assertions, pages, api, hooks, support).
• Kept the sharp edges worth knowing before editing: isOCIS in CommonAPI is hardcoded true so the OC10 branches are dead code, AndroidManager is a static singleton, and ScreenRecorder only saves video on failure.
• Added ./gradlew build -x test, the feature-file path, and the LocProperties.java pointer for local.properties keys.

Guidance that CLAUDE.md merely repeated from agents.md (OSPO policy, signed commits, DCO sign-off, Conventional Commits) was not duplicated.

One signed commit. Verify the symlink with git ls-tree HEAD — CLAUDE.md should be mode 120000 with a 9-byte blob.

Windows caveat: without core.symlinks=true plus Developer Mode, CLAUDE.md materialises as a one-line text file containing AGENTS.md. AGENTS.md itself is always correct, so nothing breaks.

🤖 Generated with Claude Code