[v0.2] Add LPP client, provider discovery, and process lifecycle

[Teakowa]

Protocol dependency: language-provider-protocol#1
Release coordination: #135

Goal

Add the Wright-owned client/runtime side of the Language Provider Protocol without importing source-language compiler ownership back into Wright.

Scope

• Consume the versioned LPP contract and conformance fixtures from wrightkit/language-provider-protocol.
• Add provider configuration/discovery by opaque language/provider identity rather than OPY/DEL-specific branches.
• Spawn and manage long-running stdio provider processes.
• Implement initialize/handshake, protocol-version checks, capability negotiation, request correlation, shutdown, timeout/process-exit/error handling, and structured diagnostics.
• Keep the client transport-neutral above the process adapter so ToolService and language services consume provider capabilities rather than raw JSON-RPC details.
• Verify interoperability against the LPP conformance/mock provider, including a deliberately non-OPY/DEL language id.
• Do not silently fall back to embedded compiler semantics when a required provider capability is unavailable.

Non-goals

• Full opy-rs or del-rs production cutover.
• Provider package management, auto-download, marketplace, or network transport.
• Exposing provider AST/HIR or Workshop internal IR.
• New source-language features.

Acceptance criteria

• Wright initializes and queries a conforming provider without OPY/DEL-specific protocol schema logic.
• Capability absence, provider failure, protocol mismatch, malformed responses, and clean shutdown are deterministic and tested.
• The LPP conformance/mock provider passes end-to-end through Wright's client path.
• Tooling layers can depend on a stable provider-client abstraction rather than process/JSON-RPC implementation details.
• No source-language compiler implementation is added to the LPP client layer.

[Teakowa]

Implemented by PR #150 (merged, commit 8fe4125). LPP v1 client crate wright-lpp with transport-neutral LanguageProvider seam, provider discovery by opaque language id, stdio process lifecycle, deterministic failure modes (spawn/exit/timeout/malformed/protocol-mismatch/capability-unavailable — explicit refusal, no silent fallback), e2e against the pinned LPP mock provider (x-demo-lang, non-OPY/DEL) 14+3 tests, CI job lpp-client-integration pins LPP commit 416b293e. QA verified independently: 12/12 CI checks green, 620 workspace tests / 0 failures. v0.2 acceptance criterion MET.