feat(extension): BYOE 0.8.0 - endpoints commands + bridge --endpoint plumbing (REQ-142)

[tbitcs]

What\n\nExtension-side companion to BitConcepts/specsmith#? (BYOE in the CLI). Adds the EndpointsClient module, two new commands, and the bridge --endpoint plumbing so VS Code sessions can be routed to a self-hosted OpenAI-v1-compatible backend registered with specsmith endpoints add.\n\n## Files\n\n- src/EndpointsClient.ts - pure-TS wrapper around specsmith endpoints list / test --json. JSON parsers (parseEndpointsList, parseEndpointHealth) and applyEndpointArg exported for direct mocha coverage. Tokens never appear in TypeScript memory; the CLI redacts inline tokens.\n- src/types.ts - SessionConfig.endpointId optional field.\n- src/bridge.ts - appends --endpoint <id> to specsmith run when SessionConfig.endpointId is set.\n- src/extension.ts - new specsmith.endpoints (Quick Pick over registered endpoints with copy-id / set-default / test actions; \\u2605 marks default) and specsmith.testEndpoint (probes /v1/models, surfaces a notification with latency + model count).\n- package.json - declares the two new commands; version 0.7.0 -> 0.8.0; description mentions BYOE OpenAI-v1 endpoints.\n- src/test/endpoints-client.test.ts - 11 new mocha tests.\n- CHANGELOG.md - cut the 0.8.0 section from [Unreleased].\n\n## Validation\n\n- npm run lint (tsc --noEmit): clean.\n- npm run build (esbuild): 279.8kb bundle.\n- npm test: 117 passing (was 104; +13 from the new suite).\n\n## How to test\n\n1. With the BYOE 0.8.0 CLI installed, register an endpoint via specsmith endpoints add.\n2. Open the command palette and run specsmith: BYOE Endpoints\\u2026 - the new endpoint appears with a \\u2605 if it is default.\n3. Pick the endpoint -> Test endpoint -> see latency / model-count notification.\n4. To route an active session: set SessionConfig.endpointId (currently via API; a Session header dropdown lands in a follow-up PR). The bridge appends --endpoint <id> to every specsmith run invocation.\n\n## Out of scope\n\n- A rich Endpoints tab in the SettingsPanel webview is deferred. The command-palette surface here is enough to drive sessions through BYOE today; a webview tab is a follow-up UI iteration.\n- Per-session UI dropdown to pick the endpoint at session-create time. The plumbing is in place via SessionConfig.endpointId; the dropdown is a small follow-up.\n\nCo-Authored-By: Oz oz-agent@warp.dev

[tbitcs]

Superseded by #47 which contains the BYOE 0.8.0 + 0.10.0 multi-agent commits and resolves the conflict against #45.