docs: add JSONL format to system_variables.md and README.md

[apstndb]

Summary

Document the JSONL output format added in #580/#581.

Key Changes

• docs/system_variables.md: Add JSONL to CLI_FORMAT valid values, usage example, --format=jsonl flag note, and type-aware JSON output description
• README.md: Add --format=jsonl to feature list and --format help text

Test plan

• make check passes
• No code changes, docs only

[github-actions]

Code Metrics Report

📊 View detailed coverage report (available for 7 days)

	main (bfe804c)	#583 (b50eb77)	+/-
Coverage	70.9%	70.8%	-0.1%
Code to Test Ratio	1:1.3	1:1.3	0.0
Test Execution Time	2m15s	1m9s	-1m6s

Details

  |                     | main (bfe804c) | #583 (b50eb77) |  +/-  |
  |---------------------|----------------|----------------|-------|
- | Coverage            |          70.9% |          70.8% | -0.1% |
  |   Files             |             78 |             78 |     0 |
  |   Lines             |           7075 |           7075 |     0 |
- |   Covered           |           5018 |           5014 |    -4 |
  | Code to Test Ratio  |          1:1.3 |          1:1.3 |   0.0 |
  |   Code              |          16419 |          16419 |     0 |
  |   Test              |          21376 |          21376 |     0 |
+ | Test Execution Time |          2m15s |           1m9s | -1m6s |

Code coverage of files in pull request scope (83.5% → 81.5%)

Files	Coverage	+/-	Status
internal/mycli/execute_sql.go	80.0%	-1.4%	affected
internal/mycli/metrics/execution_metrics.go	86.6%	-4.5%	affected

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Reported by octocov

[gemini-code-assist]

Code Review

This pull request introduces support for the JSONL (JSON Lines) output format, enabling type-aware JSON output for Spanner queries. The changes include updates to the README and system variables documentation to describe the new format and the --format=jsonl flag. A review comment identifies an inconsistency in the README's description of the JSONL format compared to the detailed documentation, specifically noting the omission of ENUM and NULL type handling, and provides a suggestion to align the two.

[Copilot]

Pull request overview

Documents the newly added --format=jsonl output mode so users can discover and correctly use JSON Lines output from the CLI.

Changes:

• Extend CLI_FORMAT documentation to include JSONL, with an example and --format=jsonl note.
• Update README feature list to mention JSONL output.
• Update the README --format help text to list jsonl as a supported value.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
docs/system_variables.md	Adds JSONL to CLI_FORMAT valid values, example usage, and notes about JSONL behavior.
README.md	Adds JSONL mentions to the feature list and updates the --format help text to include jsonl.

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[apstndb]

/gemini review

[gemini-code-assist]

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

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[apstndb]

/gemini review

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

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