feat: add endpoint and CLI for users to view their own OIDC claims (#23053)

- Adds a new API endpoint `GET /api/v2/users/oidc-claims` that returns
only the **merged claims** (not the separate id_token/userinfo
breakdown). Scoped exclusively to the authenticated user's own identity
— no user parameter, so users cannot view each other's claims.
- Adds a new CLI command:** `coder users oidc-claims` that hits the
above endpoint.
- The existing owner-only debug endpoint is preserved unchanged for
admins who need the full claim breakdown.


> 🤖 This PR was created with the help of Coder Agents, and will be
reviewed by my human. 🧑‍💻

docs/reference/cli/users_oidc-claims.md

@@ -0,0 +1,42 @@
+<!-- DO NOT EDIT | GENERATED CONTENT -->
+# users oidc-claims
+
+Display the OIDC claims for the authenticated user.
+
+## Usage
+
+```console
+coder users oidc-claims [flags]
+```
+
+## Description
+
+```console
+  - Display your OIDC claims:
+
+     $ coder users oidc-claims
+
+  - Display your OIDC claims as JSON:
+
+     $ coder users oidc-claims -o json
+```
+
+## Options
+
+### -c, --column
+
+|         |                           |
+|---------|---------------------------|
+| Type    | <code>[key\|value]</code> |
+| Default | <code>key,value</code>    |
+
+Columns to display in table output.
+
+### -o, --output
+
+|         |                          |
+|---------|--------------------------|
+| Type    | <code>table\|json</code> |
+| Default | <code>table</code>       |
+
+Output format.