fix: drop empty text blocks during projection

[kermanx]

Related Issue

No linked issue; the problem is described below.

Problem

Some providers reject empty text content blocks in request messages. Restored conversation history can replay empty streamed assistant text parts into the next provider request, causing the turn to fail before the model can continue.

What changed

• Drop empty text content parts while projecting context history for LLM requests.
• Keep the cleanup in the existing projector pass that skips partial messages and merges adjacent user messages.
• Preserve assistant tool-call messages when their empty text content is removed, because the tool call itself is still meaningful.
• Reject projected tool result messages if cleanup leaves them with empty content, rather than silently orphaning the preceding assistant tool call or synthesizing model-visible tool output.
• Add projection coverage for empty text parts, assistant tool-call messages, malformed empty tool results, encrypted thinking parts, whitespace text, and non-mutating projection behavior.

Checklist

• I have read the CONTRIBUTING document.
• I have linked a related issue, or explained the problem above.
• I have added tests that prove my feature works.
• Ran gen-changesets skill, or this PR needs no changeset.
• Ran gen-docs skill, or this PR needs no doc update.

Validation

• pnpm vitest run packages/agent-core/test/agent/context.test.ts
• pnpm exec oxlint --type-aware packages/agent-core/src/agent/context/projector.ts packages/agent-core/test/agent/context.test.ts
• git diff --check -- packages/agent-core/src/agent/context/projector.ts packages/agent-core/test/agent/context.test.ts
• Read-only diff audit found no new internal identifiers, credentials, real endpoints, or other public-text leaks.

[changeset-bot]

🦋 Changeset detected

Latest commit: a328707

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@moonshot-ai/kimi-code	Patch

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[pkg-pr-new]

pnpm dlx https://pkg.pr.new/@moonshot-ai/kimi-code@a328707

npx https://pkg.pr.new/@moonshot-ai/kimi-code@a328707

commit: a328707

[chatgpt-codex-connector]

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[kermanx]

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[kermanx]

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[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Swish!

Reviewed commit: a328707a78

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