refactor: 移除 MicroCompact 子系统

[Yumiue]

概述

本 PR 彻底移除 MicroCompact 子系统，降低上下文管理模块的复杂度，明确 compact 策略的单一职责。

Closes #706

变更内容

删除文件（9 个，约 2200 行）

文件	说明
internal/context/microcompact.go	核心压缩逻辑
internal/context/microcompact_test.go	单元测试
internal/context/microcompact_summarizer_test.go	summarizer 测试
internal/context/pin_checker.go	pin 检查器
internal/context/pin_checker_test.go	pin 检查器测试
internal/tools/micro_compact_policy.go	policy 定义
internal/tools/micro_compact_summarizer.go	summarizer 接口
internal/tools/micro_compact_summarizer_test.go	summarizer 测试
internal/tools/micro_compact_summarizers_builtin.go	内置 summarizer 实现

修改文件（约 20 个）

• internal/context/types.go — 移除 MicroCompact 相关类型与字段
• internal/context/builder.go — 移除 microcompact 引用与构建逻辑
• internal/context/projection.go — 移除 microcompact 投影逻辑
• internal/config/context.go — 移除 microcompact 配置项
• internal/config/loader.go — 移除配置加载中的 microcompact 分支
• internal/tools/manager.go — 移除 summarizer 注册
• internal/tools/registry.go — 移除 microcompact 工具注册
• internal/runtime/runtime.go — 移除 runtime 中的 microcompact 引用
• internal/app/bootstrap.go — 移除启动时的 microcompact 初始化
• docs/context-compact.md — 移除 microcompact 相关文档
• docs/tech-debt.md — 更新技术债务清单
• docs/roadmap.md — 更新路线图
• 各工具文件 — 移除 microcompact 相关的 import 与引用

影响分析

• 编译：go build ./... 通过 ✅
• 测试：go test ./... 通过 ✅
• 主链路：无影响，microcompact 未被 runtime 主链路调用
• 配置：microcompact 配置项已移除，不影响其他配置加载
• 文档：已同步更新，无残留引用

测试计划

• go build ./... 编译通过
• go test ./... 全部通过
• go vet ./... 无警告
• grep 确认无残留 microcompact 引用
• 相关文档已同步更新

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[codecov]

Codecov Report

❌ Patch coverage is 93.75000% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/context/projection.go	86.66%	1 Missing and 1 partial ⚠️

📢 Thoughts on this report? Let us know!

[fennoai]

Review found two noteworthy issues: one read-time context bounding regression and one formatting regression. Targeted tests passed with go test ./internal/context ./internal/config ./internal/runtime ./internal/tools.

[fennoai]

With micro-compact removed, this path now projects every retained tool result at full DefaultOutputLimitBytes size. The default read_time_max_message_spans=24 can therefore send many 64 KiB tool outputs back through prompt estimation/provider calls, and it also keeps sensitive tool output visible longer than before. Please keep a read-time per-tool excerpt/sanitization step here (similar to the recent/memo projection) or otherwise bound projected tool content after trimming.

[fennoai]

This block is not gofmt-formatted (the assignment and closing brace are over-indented). Running gofmt also changes several nearby files touched by this PR, so please format the changed Go files before merging.