feat(api): Read the API base path from the spec's server URL - #20787

…148)

**Merge order:**
[#148](#148)
→
[getsentry/sentry-docs#20787](getsentry/sentry-docs#20787)
→
[getsentry/sentry#131065](getsentry/sentry#131065)
→ the getsentry/toolkit bump, after `@sentry/api` 2.0.0 is published.
Docs has to merge before sentry#131065. When that merges, the spec sync
commits the new spec to sentry-api-schema, which auto-releases
`@sentry/api` and auto-bumps the schema in sentry-docs. Without
sentry-docs#20787 merged first, the docs would drop `/api/0` from paths
and curl examples. This PR supersedes #147, which hard-coded
`API_PREFIX`.

Per @BYK, the server decides the base path. `/api/0` comes from the
spec's server URL. It's exported as `API_BASE_PATH`, and every path in
the package is relative to it. Nothing here hard-codes `0`. A future
`/api/1` spec would produce `API_BASE_PATH = "/api/1"` with no code
change.

**Design**
- `lib/api-base-path.mjs` reads the base path from the path of
`servers[0].url`, makes `paths` relative, and trims server URLs to their
origin. That includes the per-operation override on `listSeerModels`.
- **Until the sentry PR lands,** the base path is the `/api/<version>`
prefix that every path shares. It's marked TODO. Both spec shapes build
the same `src/`; I checked this with `diff -r`. So the sentry change
only syncs a byte-identical package through the bot.
- **`baseUrl` stays the Sentry origin.** That's what users have,
including self-hosted URLs and `links.regionUrl`. The patched `buildUrl`
builds the request URL as origin + `API_BASE_PATH` + operation path.
- **Exported** from `@sentry/api`, `@sentry/api/client` and
`@sentry/api/operations`.
- **The four `/api/0` copies are gone:** in `core.ts`,
`buildSentryApiUrl`, `parseApiPathScope` and cache invalidation. So are
the copies in the idempotent matcher, `normalize-spec` and
`source-analysis`. Matching still finds the base path anywhere in the
URL, as before.

**Before / After**
```ts
// @sentry/api/operations
{ functionName: "listOrganizations", path: "/api/0/organizations/" }
{ functionName: "listOrganizations", path: "/organizations/" }

import { API_BASE_PATH } from "@sentry/api"; // "/api/0", from servers[0].url

// raw requests: url is relative to API_BASE_PATH
sentry.client.prepareRequest({ method: "GET", url: "/api/0/organizations/" }); // before
sentry.client.prepareRequest({ method: "GET", url: "/organizations/" });       // after
// both send https://sentry.io/api/0/organizations/
```

**Breaking: major bump to 2.0.0**
- `operations[].path` and `IdempotentOperation.path` are relative.
Build-time lists derived from the catalog must be regenerated, such as
toolkit's `idempotent-operations.json`.
- Raw `client.request`, `client.get` and `prepareRequest` take relative
`url`s. An old `/api/0/...` URL now gets a doubled base path.
- Generated function names, types and the request URLs of typed
operations don't change: `sentry-client.gen.ts` is byte-identical.

Co-Authored-By: BYK <126780+BYK@users.noreply.github.com>

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via @BYK.
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Co-authored-by: sentry-junior[bot] <264270552+sentry-junior[bot]@users.noreply.github.com>
Co-authored-by: BYK <126780+BYK@users.noreply.github.com>