Add CLI read-field discovery and bounded local output formats

[LIghtJUNction]

Refs #82. Adds a coherent read-output slice on main cd81710, including the merged #196 through a history-preserving merge.

msg call gains explicit --contract-version (default 1 preserved) and --json [FIELDS]. Bare --json lists selectable fields from the exact server Registry input schema without executing the business query. Explicit fields become signed server-side arguments; cursor/duplicate projection conflicts and non-read contracts refuse before business execution. No guessed field vocabulary or client-side full-result truncation.

Optional --jq uses installed jq through fixed argv/no shell, empty environment and temporary module directory, conservative module refusal, streamed 1 MiB output bound and 2-second timeout with child cleanup. --template supports only JSON-pointer placeholders with JSON-escaped substitutions, no expression evaluation or attribute access. Both require explicit nonempty --json. Query/template input limits and failure codes are documented in docs/CLI_FIELD_SELECTION.md. jq intermediate memory follows host process limits; these I/O/time limits are not a general resource sandbox.

Validation: 12 initial field-selection regressions failed before implementation; 12 initial formatting regressions likewise failed before implementation. Final 36 pure tests and 61 existing related client/TUI tests pass locally with Python 3.15. Full Ruff/608-file format/warnings-as-error compile, pinned uv 0.12.20 wheel+sdist and package-content verification pass. Independent code review found no concrete blocker and verified overflow/cancellation cleanup. New real signed HTTP/PostgreSQL test covers field discovery, projection, jq/template output, cursor continuation and all-row zero-write checks; local execution is blocked by the environment's PostgreSQL socket restriction, so this and full contracts/deployment gates must pass in CI.

Only 5 files change; final tree 7b1f45a5d6879943fa9a8d4f513349abd2c7ef5f at head e8e3ec0. No merge/deployment request. No global shortcut formatting or automatic pagination is claimed, and #82 stays open. Existing authentication, signatures, mutations and default JSON output remain unchanged. Both original CLI and #196 histories are preserved; no force update was used. Final-tree CI is required.

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
🔒 Security Review	✅ Completed 2026-09-30T13:41:33.044229Z	e8e3ec0	Draft marked ready

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.

[LIghtJUNction]

最终验证已收齐。当前 main 817cdec687fe05974c11b762f65ed7fd1638bfe1 的 tree 7b1f45a5d6879943fa9a8d4f513349abd2c7ef5f 与本 PR 最终候选完全一致。

• PR head e8e3ec06：12 个适用工作流全部 success；完整回归 36721271572 的 8 个 shards 和最终 contracts 均通过。
• 独立 main push：7 个适用工作流全部 success；完整回归 36721920259、质量 36721920206、安装包隔离演练 36721920237 分别有独立运行证据。
• 两次完整运行的 16 份 shard ZIP 均下载并核对 SHA-256。逐一核验 manifest/JUnit 精确 node ID：各为 2699 core + 8 conformance，完整互斥并集，零 failure/error/skipped。不是仅比较总数。
• 新增 CLI 的 37 个用例两次均通过；真实签名 HTTP/PostgreSQL 字段发现、字段下推、jq/template、cursor 续读及全表零写入用例在两次 shard 3 中分别用时 6.144s / 5.911s，已读取 JUnit 确认。

本 PR 的字段选择和有限本地输出切片已在主线。其他快捷命令的通用输出、自动分页及 #82 的其余条款仍开放；没有把隔离 CI 描述为生产部署。