fix(opencode): Map bicep file extensions to language ids for custom LSP usage

[DrBushyTop]

Issue for this PR

Closes #15569

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Fixes missing Bicep diagnostics in custom LSP setups by sending the correct language IDs for Bicep files.

• Adds extension-to-language mappings in packages/opencode/src/lsp/language.ts:
  • .bicep -> bicep
  • .bicepparam -> bicep-params
• Ensures textDocument/didOpen uses Bicep language IDs instead of falling back to plaintext, allowing Bicep LSP to publish diagnostics.

How did you verify your code works?

• Set opencode.json config to

"lsp": {
  "bicep": {
    "extensions": [
      ".bicep",
      ".bicepparam"
    ],
    "command": [
      "dotnet",
      "/Users/pasi/.opencode-lsp/bicep-langserver/Bicep.LangServer.dll"
    ]
  }
},

• Built local binary from source:
  • bun run build --single in packages/opencode
• Ran diagnostics with the built binary against an invalid .bicep file:
  • dist/opencode-darwin-arm64/bin/opencode debug lsp diagnostics .development/tmp-bicep-lsp-test.bicep --print-logs --log-level DEBUG
• Verified diagnostics are now returned (e.g., BCP007) and logs show textDocument/publishDiagnostics for the .bicep file.

INFO  2026-03-01T12:27:39 +1ms service=lsp serverIds=SNIPPED..., bicep enabled LSP servers
INFO  2026-03-01T12:27:39 +0ms service=file.watcher init
INFO  2026-03-01T12:27:39 +1ms service=scheduler id=snapshot.cleanup run
INFO  2026-03-01T12:27:39 +0ms service=scheduler id=tool.truncation.cleanup run
INFO  2026-03-01T12:27:39 +0ms service=bus type=command.executed subscribing
INFO  2026-03-01T12:27:39 +1ms service=file.watcher platform=darwin backend=fs-events watcher backend
INFO  2026-03-01T12:27:39 +147ms service=lsp file=.development/tmp-bicep-lsp-test.bicep touching file
INFO  2026-03-01T12:27:39 +2ms service=lsp serverID=bicep spawned lsp server
INFO  2026-03-01T12:27:39 +0ms service=lsp.client serverID=bicep starting client
INFO  2026-03-01T12:27:39 +1ms service=lsp.client serverID=bicep sending initialize
INFO  2026-03-01T12:27:39 +2ms service=vcs branch=main initialized
INFO  2026-03-01T12:27:39 +0ms service=bus type=file.watcher.updated subscribing
INFO  2026-03-01T12:27:39 +240ms service=lsp.client serverID=bicep initialized
INFO  2026-03-01T12:27:39 +0ms service=bus type=lsp.updated publishing
INFO  2026-03-01T12:27:39 +0ms service=lsp.client serverID=bicep path=/Users/pasi/Code/.development/tmp-bicep-lsp-test.bicep waiting for diagnostics
INFO  2026-03-01T12:27:39 +0ms service=bus type=lsp.client.diagnostics subscribing
INFO  2026-03-01T12:27:39 +1ms service=lsp.client serverID=bicep path=/Users/pasi/Code/.development/tmp-bicep-lsp-test.bicep workspace/didChangeWatchedFiles
INFO  2026-03-01T12:27:39 +0ms service=lsp.client serverID=bicep path=/Users/pasi/Code/.development/tmp-bicep-lsp-test.bicep textDocument/didOpen
INFO  2026-03-01T12:27:39 +198ms service=snapshot prune=7.days cleanup
INFO  2026-03-01T12:27:39 +93ms service=lsp.client serverID=bicep path=/Users/pasi/Code/.development/tmp-bicep-lsp-test.bicep count=1 textDocument/publishDiagnostics
INFO  2026-03-01T12:27:39 +0ms service=bus type=lsp.client.diagnostics publishing
INFO  2026-03-01T12:27:40 +150ms service=lsp.client serverID=bicep path=/Users/pasi/Code/.development/tmp-bicep-lsp-test.bicep got diagnostics
INFO  2026-03-01T12:27:40 +1ms service=bus type=lsp.client.diagnostics unsubscribing
INFO  2026-03-01T12:27:40 +0ms service=bus type=lsp.client.diagnostics unsubscribing
{
  "/Users/pasi/Code/.development/tmp-bicep-lsp-test.bicep": [
    {
      "range": {
        "start": {
          "line": 2,
          "character": 0
        },
        "end": {
          "line": 2,
          "character": 4
        }
      },
      "severity": 1,
      "code": "BCP007",
      "codeDescription": {
        "href": "https://aka.ms/bicep/core-diagnostics#BCP007"
      },
      "source": "bicep",
      "message": "This declaration type is not recognized. Specify a metadata, parameter, variable, resource, or output declaration."
    }
  ]
}

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

Hey! Your PR title Map bicep file extensions to language ids for custom LSP usage doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.