Closes CODAGT-157 (in part).

Coder Agents is moving from Early Access to Beta for the May release. This PR:

1. Renames every “Early Access” reference in the /agents docs to “Beta” (prose, manifest nav titles, and state badges).
2. Deletes the standalone docs/ai-coder/agents/early-access.md page and its nav entry. The Beta positioning stays in place via the existing Product status section in index.md and the lead callout in getting-started.md.

Scope

• Deleted: docs/ai-coder/agents/early-access.md (whole page, 85 lines).
• Updated: docs/ai-coder/agents/index.md — “Product status” paragraph: drop the link to the deleted page; keep the Beta sentence.
• Updated: docs/ai-coder/agents/getting-started.md — lead [!NOTE] callout, “Things to know” paragraph, and the redundant “See [Enable Coder Agents]” pointer (Step 1 already inlines the same CODER_EXPERIMENTS instructions).
• Updated: docs/manifest.json — 14 state badges flipped to beta; removed the “Early Access” nav entry that pointed to the deleted page.

Unrelated "early access" entries elsewhere in the manifest (User Secrets, External Workspaces, Startup Dependencies, AI Gateway MCP Tools Injection) are intentionally untouched.

What we lose by deleting the page

Flagging this so reviewers can decide:

• The “What Beta does not include” list (no SLA, no stability guarantees, etc.).
• The Beta-to-GA licensing notice.
• The standalone enablement walkthrough that ´getting-started.md´ already covers.
• The “Providing feedback” paragraph (also covered in getting-started.md).

If any of this needs to live somewhere, happy to migrate it into getting-started.md or index.md in a follow-up.

URLs

Deleting the file removes /docs/ai-coder/agents/early-access. The redirect to /agents/getting-started (or /agents/) belongs in the coder.com docs site config, not this repo. I will open the corresponding redirect PR there separately.

Proof

This is a docs-text change with no behavior change. Visible string diffs:

index.md — Product status section, link removed

 Coder Agents is in Beta. The feature is under active development and
-available for evaluation. See [Beta](./early-access.md) for
-enablement instructions and program details.
+available for evaluation.

getting-started.md — lead callout, link removed

 > [!NOTE]
-> Coder Agents is in [Beta](./early-access.md). Deploy to a
+> Coder Agents is in Beta. Deploy to a
 > **test or development environment** — not production — while evaluating
 > the feature.

getting-started.md — redundant “See [Enable Coder Agents]” pointer dropped

 CODER_EXPERIMENTS="agents,oauth2,mcp-server-http" coder server

-See Enable Coder Agents for full
-details.

Step 2: Configure an LLM provider and model

**`manifest.json` — nav entry removed**

```diff
 {
     "title": "Getting Started",
     ...
 },
-{
-    "title": "Beta",
-    "description": "About the Coder Agents Beta program",
-    "path": "./ai-coder/agents/early-access.md",
-    "state": ["beta"]
-},
 {
     "title": "Architecture",
     ...
 }

Screenshots of the rendered Beta pages from before the deletion are attached to the chat. After this PR the standalone Beta page is gone, so the in-product proof is the unchanged Beta badges in the navigation and the surviving Beta callout in getting-started.md.

Validation

• pnpm exec markdownlint-cli2 docs/ai-coder/agents/index.md docs/ai-coder/agents/getting-started.md → 0 errors
• python3 -m json.tool docs/manifest.json → valid JSON
• bash scripts/check_emdash.sh → OK, no new emdash/endash characters
• grep -rn -E "early.access|early-access" docs/ai-coder/agents/ docs/manifest.json → only the four unrelated state: ["early access"] matches outside /agents, intentionally untouched

Follow-ups (out of scope here)

• Redirect from /docs/ai-coder/agents/early-access to /docs/ai-coder/agents/getting-started in the coder.com docs site repo.
• The deeper docs audit against the Chats API implementation (auto-archive default, missing endpoints, missing attach_file tool, etc.) is tracked separately and will be a follow-up PR against CODAGT-157.

Coder Agent generated this PR on @david-fraley's behalf.