D755 — Claude config dirs are declared, not discovered

Decision. clients.claude.config_dirs in .cartographer.yaml lists extra Claude Code config directories (each holding its own .claude.json, as under CLAUDE_CONFIG_DIR); sync and connect write and remove the cartographer MCP entries in $HOME plus every declared directory. Only those entries fan out: KB-provided mcp artifacts, skills, agents, hooks, CLAUDE.md and the bootstrap hook stay $HOME-relative.

Why. After a KB rename every account kept the stale URL, because nothing wrote outside ~/.claude.json. Sync also runs from session-start hooks (inheriting one account's environment) and from the timer (inheriting none), so a target set read from the environment would change from run to run and orphan entries. An undeclared CLAUDE_CONFIG_DIR is only a warning naming the key to add. The cost: a new account needs one line in the file.

Alternatives rejected. - Discover from CLAUDE_CONFIG_DIR at sync time: flip-flops the set between hook, timer and shell runs. - Reuse BaseDirEnv: it replaces the root instead of adding roots, and Claude's layout ($DIR/.claude.json) is not $DIR/.claude/.... - Fan out every artifact kind: needs multi-root lockfile projections; users symlink those directories instead.

Consequences. ClientBinding is an explicit binding only when it carries a kbs key (KBsSet): an entry holding just config_dirs leaves the provider on the default KB set, never default-deny. config_dirs under any provider but claude is a load error. A declared directory that is missing, relative or holds a non-regular .claude.json is skipped with a warning, never created.