feat(core): configRead {kind,name} — complete the configList registry contract (T-401)

[matze4u]

What

Completes the configList agent-config registry contract (ADR-050) with its read sibling, configRead {kind, name} → {kind, name, source, body}. This mirrors the commandList + commandRead PAIR (ADR-048) — the command council had explicitly required BOTH because a list whose items the IDE cannot open into a detail pane is "half a contract". configList was exactly that half-contract for skills + rules + commands.

How

• Protocol — ConfigReadRequest {kind,name}, ConfigReadResponse {kind,name,source,body}, and a local-only ConfigSource enum ('local' | 'missing', no mcp member, unlike CommandSource). Registered configRead in the Methods registry + hand-maintained codegen descriptors (67 → 69 Kotlin DTOs).
• Core — ConfigHandler.read reads the body straight off the same walk-once cache configList groups, so list and read can never disagree. Local-only by design: the body is already parsed onto every walked node for all three kinds; MCP has skill_read/command_read but no rule_read, so an MCP-first path would be asymmetric. A miss is source: 'missing' with an empty body (no throw, mirrors commandRead). Matching is on the display name (frontmatter name ?? slug) via a shared displayName helper, so list/read key identically. Dispatcher route behind the existing requireConfig() gate.

Council

codex-cli 0.134.0 + gemini-cli 0.41.2, run serially. UNANIMOUS Q0–Q3 = A: wire now (complete the contract) / {kind,name} key (names collide across kinds) / local-only / mirror commandRead. Q4 → full body uncapped (consistency with commandRead). Q5 traps satisfied by design (shared walk cache → no disagreement; in-memory match → no path traversal).

Verification

• task ci exit 0 — lint, format, build, typecheck, test (core 1147 pass / 1 skip, +15).
• task jetbrains:check BUILD SUCCESSFUL (the +2 Kotlin DTOs compile).
• No checkbox flip — the skill picker / rules viewer detail-pane render remains an IDE surface; this is the headless body data path it will call.

See ADR-052.