Consolidate blinkagent[bot] and blink-so[bot] into a single identity

## Problem

Blink-created PRs and commits show two different bot identities:
- **blinkagent[bot]** - the GitHub App that pushes commits and creates PRs
- **blink-so[bot]** - set as `GIT_AUTHOR_NAME`/`GIT_COMMITTER_NAME` in the CLI, appears in `Co-authored-by` trailers

This causes confusion as users see both identities attributed to the same commit.

## Current Behavior

In `packages/blink/src/cli/connect.ts` (and `compute-server.ts`), the CLI sets:
```typescript
process.env.GIT_AUTHOR_NAME = "blink-so[bot]";
process.env.GIT_AUTHOR_EMAIL = "211532188+blink-so[bot]@users.noreply.github.com";
process.env.GIT_COMMITTER_NAME = "blink-so[bot]";
process.env.GIT_COMMITTER_EMAIL = "211532188+blink-so[bot]@users.noreply.github.com";
```

When the GitHub App (`blinkagent[bot]`) pushes these commits, GitHub shows both identities.

## Proposal

Consolidate to a single identity for cleaner attribution. Options:
1. Use the same identity (`blinkagent[bot]` or `blink-so[bot]`) for both the CLI git config and the GitHub App
2. Remove the `Co-authored-by` trailer if it's redundant

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Created on behalf of @matifali and @hugodutka