feat(coverage): default to text reporter skipFull if agent detected

[hi-ogawa]

Description

• (slightly) related MCP server for test results and coverage #8411

I was prototyping a new text-agent coverage reporter, which skips 100% coverage just like test agent reporter (#9779) skips passing tests. But then I noticed text coverage reporter already supports skipFull which does mostly same.

This PR auto enables skipFull when the agent is detected.
(EDIT: and also auto configure text-summary, so it has aggregated stats to avoid ended up with empty output.)

• without agent

~/code/others/vitest $ pnpm -C examples/fastify test --coverage 
...
 DEV  v4.1.2 /home/hiroshi/code/others/vitest/examples/fastify
      Coverage enabled with v8

 ✓ test/app.test.ts (3 tests) 55ms
   ✓ with HTTP injection 15ms
   ✓ with a running server 13ms
   ✓ with axios 25ms

 Test Files  1 passed (1)
      Tests  3 passed (3)
   Start at  19:18:31
   Duration  465ms (transform 39ms, setup 0ms, import 294ms, tests 55ms, environment 0ms)

 % Coverage report from v8
--------------|---------|----------|---------|---------|-------------------
File          | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
--------------|---------|----------|---------|---------|-------------------
All files     |     100 |      100 |     100 |     100 |                   
 fastify      |     100 |      100 |     100 |     100 |                   
  mockData.ts |     100 |      100 |     100 |     100 |                   
 fastify/src  |     100 |      100 |     100 |     100 |                   
  app.ts      |     100 |      100 |     100 |     100 |                   
--------------|---------|----------|---------|---------|-------------------
 PASS  Waiting for file changes...
       press h to show help, press q to quit

• with agent

~/code/others/vitest $ AI_AGENT=true pnpm -C examples/fastify test --coverage 
...
 RUN  v4.1.2 /home/hiroshi/code/others/vitest/examples/fastify
      Coverage enabled with v8


 Test Files  1 passed (1)
      Tests  3 passed (3)
   Start at  19:18:37
   Duration  295ms (transform 35ms, setup 0ms, import 129ms, tests 49ms, environment 0ms)

 % Coverage report from v8
--------------|---------|----------|---------|---------|-------------------
File          | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
--------------|---------|----------|---------|---------|-------------------
--------------|---------|----------|---------|---------|-------------------
=============================== Coverage summary ===============================
Statements   : 100% ( 4/4 )
Branches     : 100% ( 0/0 )
Functions    : 100% ( 1/1 )
Lines        : 100% ( 4/4 )
================================================================================

Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

• It's really useful if your PR references an issue where it is discussed ahead of time. If the feature is substantial or introduces breaking changes without a discussion, PR might be closed.
• Ideally, include a test that fails without this PR but passes with it.
• Please, don't make changes to pnpm-lock.yaml unless you introduce a new test example.
• Please check Allow edits by maintainers to make review process faster. Note that this option is not available for repositories that are owned by Github organizations.

Tests

• Run the tests with pnpm test:ci.

Documentation

• If you introduce new functionality, document it. You can run documentation with pnpm run docs command.

Changesets

• Changes in changelog are generated from PR name. Please, make sure that it explains your changes in an understandable manner. Please, prefix changeset messages with feat:, fix:, perf:, docs:, or chore:.

[netlify]

✅ Deploy Preview for vitest-dev ready!

Built without sensitive environment variables

Name	Link
🔨 Latest commit	a5c563a
🔍 Latest deploy log	https://app.netlify.com/projects/vitest-dev/deploys/69c9c7d71dfd940008991b21
😎 Deploy Preview	https://deploy-preview-10018--vitest-dev.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[AriPerkkio]

Good idea but I wonder if it confuses agents or humans to see empty reports.

text reporter should probably print something like ... and 50 files with 100% coverage. 🤔

[hi-ogawa]

Good idea but I wonder if it confuses agents or humans to see empty reports.

text reporter should probably print something like ... and 50 files with 100% coverage. 🤔

We can also ensure text-summary at the same time, but this still doesn't show file stats. Any customization beyond this requires Vitest's own builtin coverage reporters.

 % Coverage report from v8
--------------|---------|----------|---------|---------|-------------------
File          | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
--------------|---------|----------|---------|---------|-------------------
--------------|---------|----------|---------|---------|-------------------

=============================== Coverage summary ===============================
Statements   : 100% ( 4/4 )
Branches     : 100% ( 0/0 )
Functions    : 100% ( 1/1 )
Lines        : 100% ( 4/4 )
================================================================================