Migrate tile.json to .tessl-plugin/plugin.json

[jimutt]

Why

tile.json is deprecated. Every tessl invocation warns:

tile.json is deprecated. Migrate to .tessl-plugin/plugin.json to publish a plugin-shape package. tile.json support will be removed in a future release.

It's also a prerequisite for evals: tessl eval run <plugin-dir> looks for .tessl-plugin/plugin.json, so scenario evaluation can't run against the tile-shaped package.

Kept separate from the eval work so the packaging change can be reviewed on its own.

What changed

• tessl plugin migrate generated .tessl-plugin/plugin.json. Skills became directory references (skills/dld-common) rather than SKILL.md paths, steering became rules, and summary became description.
• tile.json deleted. With both present the linter reports plugin.json as authoritative and tile.json as ignored, with the packaged tarball synthesised from plugin.json — so leaving it would let it drift silently.
• CLAUDE.md updated: directory structure, the dual-directory section, the packaging section, and the tessl tile lint → tessl plugin lint convention. Also corrects a stale version reference (dld-kit/dld@0.1.0).
• Three manifest tests rewritten against plugin.json, plus a new test asserting plugin.json exists and tile.json is gone.

Test fix worth noting

Two of the replaced tests could not fail. Their return 1 ran inside a while loop on the right-hand side of a pipe, which bash runs in a subshell:

grep '"path":' "$REPO_ROOT/tile.json" | sed '...' | while IFS= read -r path; do
  if [[ ! -f "$REPO_ROOT/$path" ]]; then
    echo "..."
    return 1     # subshell — never fails the test
  fi
done

The replacements read entries into an array with mapfile first, and assert the parse produced at least one entry so an empty or renamed manifest fails loudly instead of passing on zero iterations.

Verification

• tessl plugin lint — valid, deprecation warning gone
• tessl plugin pack — tarball builds
• 166/166 bats tests pass
• Negative control: restoring tile.json makes the new test fail as intended

🤖 Generated with Claude Code