feat(memory): /init generates standard AGENTS.md with exploration-first prompt

[topcheer]

Summary

User-directed change (3 parts):

1. Repo's own memory file → standard AGENTS.md: GGCODE.md renamed to AGENTS.md (content unchanged, history preserved); GGCODE.md kept as a thin compat stub (one-liner pointer) so legacy lookups still work without duplicate context injection.

2. /init now generates AGENTS.md: DefaultProjectMemoryFilename → "AGENTS.md"; startup "create memory?" prompt and /init target AGENTS.md. The loader still reads all four filenames (GGCODE.md / AGENTS.md / CLAUDE.md / COPILOT.md) — full backward compatibility; startup prompt only triggers when NONE exist.

3. Exploration-first /init prompt (fixes the "template dump" problem): the old prompt handed the agent a pre-baked heuristic document to write verbatim. The new prompt instructs the agent to FIRST understand the repository (README, build manifests, entrypoints, Makefile/CI, representative sources) and THEN write AGENTS.md from what it actually found; the heuristic snapshot (detected paths/validation/conventions) is demoted to a verify-first hint block.

Files

• GGCODE.md → AGENTS.md (rename) + compat stub
• internal/memory/project.go — default filename const
• internal/memory/init.go — template header # AGENTS.md, comments
• internal/tui/commands.go — exploration-first prompt
• internal/tui/ — i18n (11 languages), completion, comments; four-filename enumeration strings untouched
• internal/memory/project_test.go — target assertion updated

Validation

• go build -tags goolm ./... OK
• go test -tags goolm ./internal/memory/ OK (incl. TestResolveProjectMemoryInitTarget with new default)
• go test -tags goolm ./internal/tui/ OK (full package, i18n catalogs)
• gofmt -l clean

Note: opened while PR throttle window shows 6 open PRs — this is a direct user request, not an issue-round fix.

[topcheer]

合并说明：techwriter_techwriter222_agent 代裁 approve（reviewer 作者回避；四复核：GGCODE.md→AGENTS.md 逐字迁移零丢失+stub 指向/四文件名枚举保留 GGCODE.md 仍优先/exploration-first prompt 全只读匹配含 plan 模式/i18n 11 语言 en fallback）。CI 9/9。执行合并。