[Feature]: Link a GLM Coding Plan API key in AI Provider Accounts

[parkavenue9639]

Problem or use case

Since #23520 the status bar can show the GLM Coding Plan quota, but the only credential source is the ZCode CLI's ~/.zcode/cli/config.json. Plenty of GLM Coding Plan subscribers (both the international Z.AI console and Zhipu's mainland BigModel platform) never install the ZCode CLI — they run GLM through Claude Code (ANTHROPIC_BASE_URL=https://api.z.ai/api/anthropic or https://open.bigmodel.cn/api/anthropic), OpenCode, or Cline. For them:

• Settings → AI Provider Accounts has no GLM section at all (MiniMax has cookie + API key entry; GLM has nothing), so there is no way to link the plan from inside Orca.
• The status-bar meter is also PATH-gated on the ZCode CLI, so even with credentials available there is no meter without the CLI installed.

Both sites expose the same quota endpoint (/api/monitor/usage/quota/limit, raw Authorization key), so one credential flow covers both — the user just has to pick which site their plan belongs to.

Proposed solution

Add a GLM Coding Plan section to Settings → AI Provider Accounts:

• A site selector — Z.AI (z.ai) vs Zhipu BigModel (open.bigmodel.cn) — persisted like minimaxEndpoint.
• An API key field stored through the existing per-provider safeStorage envelope pattern (MiniMax API-key store), never crossing IPC back to the renderer.
• The saved key takes priority over ~/.zcode/cli/config.json, so the existing ZCode-CLI flow keeps working unchanged as a fallback.
• Config-hash invalidation + fetch-generation guards mirror MiniMax, so switching site/key discards the stale snapshot instead of showing the other site's quota.
• When a plan key is saved, the zcode status-bar meter is exempt from ZCode CLI PATH detection (same exemption MiniMax/Cursor already have), so the meter appears without the CLI.

Related: #18506 (status-bar quota, delivered by #23520), #7569 (broader custom-provider quota visibility).

[nwparker]

Completed by merged #24618 (#24618): Settings → AI Provider Accounts now links a GLM Coding Plan key for Z.AI or BigModel without installing ZCode, keeps the key in the execution-host protected store, and feeds the existing quota/status pipeline with saved-key priority and stale-refresh rejection. Credit to @parkavenue9639 for #23804. Independent source checks and hidden UI proof passed; authenticated native-platform and broader OAuth/model work are separate from this account-linking request.