docs(vx): state which inspection commands support --json

[jackylee-ch]

query.md said all inspection commands support --json. vx segments has no such flag (it always
prints JSON) and vx tree array accepts it then prints a human tree, so a script trusting it breaks
either way. Wiring vx tree array changes CLI output, so that is left for an issue.

Also adds query and segments to the vx README, which listed four of six subcommands.

Tests

make -C docs html succeeds under --fail-on-warning, same warning count as develop.

AI assistance

Written with agentic AI assistance; I read each command's argument struct first.

[codspeed-hq]

Merging this PR will regress 1 benchmark

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 4 improved benchmarks
❌ 1 regressed benchmark
✅ 2107 untouched benchmarks
⏩ 106 skipped benchmarks¹
🗄️ 4 archived benchmarks run²

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	WallTime	arrow_checked_add_u32_avx2[16384]	17.7 µs	21.3 µs	-16.76%
⚡	WallTime	arrow_checked_add_u32_avx512[16384]	21.3 µs	17.6 µs	+20.73%
⚡	Simulation	take[duplicates/repeated/primitive/nonnull/chunks=16/indices=1000]	245 µs	207 µs	+18.39%
⚡	WallTime	words_gather_scalar_avx2[65536]	9.5 µs	8.2 µs	+14.77%
⚡	WallTime	mul_u32_nonnull_avx512	6.3 µs	5.7 µs	+10.73%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing jackylee-ch:vx-json-docs (2466e23) with develop (ee1ac25)}

Footnotes

1. 106 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. 4 benchmarks were run, but are now archived. If they were deleted in another branch, consider rebasing to remove them from the report. Instead if they were added back, click here to restore them. ↩