fix(lint): add tests for ::: (unhide) visibility

[julienduchesne]

Summary

• Adds a test fixture testdata/clean/triple_colon_visibility.jsonnet covering object fields with ::: (Jsonnet "unhide") visibility
• Adds three inline unit tests in jrsonnet-lint/src/lib.rs:
  • lint_snippet_triple_colon_visibility_no_parse_error — attribute::: 'value' must not produce parse errors or diagnostics
  • lint_snippet_triple_colon_local_used_no_false_positive — a local used only in a ::: field value must not be reported as unused
  • lint_snippet_triple_colon_plus_modifier_no_parse_error — field+::: (merge + unhide) must parse and lint cleanly

Test plan

• cargo check --tests -p jrsonnet-lint passes (confirms code compiles)
• cargo test -p jrsonnet-lint passes on CI (all three new tests green)
• No regressions in existing lint tests

🤖 Generated with Claude Code

[github-actions]

Benchmark Results

Benchmark	Test	vs tk	vs base
Diff	cluster_scoped	46.88x faster	equal
Diff	configmap_unchanged	26.79x faster	equal
Diff	deployment_nested_changes	26.51x faster	equal
Env List	Single Inline Directory (--json)	44.63x faster	equal
Env List	Single Inline File (--json)	44.49x faster	equal
Env List	All Environments (--json)	85.47x faster	equal
Eval	Single Static Environment	15.06x faster	equal
Eval	Inline Environment File	22.92x faster	equal
Eval	Eval Expression - Deeply Nested Path	15.3x faster	equal
Export (Full)	Single Static Environment	5.45x faster	equal
Export (Full)	Single Inline Environment	14.09x faster	equal
Export (Full)	All Environments	11.26x faster	equal
Export (Replace)	Single Static Environment	5.17x faster	equal
Export (Replace)	Single Inline Environment	16.78x faster	equal
Export (Replace)	All Environments	19.45x faster	equal
Tool Importers Count	Single Lib Directory (Non-Recursive)	2.12x faster	equal
Tool Importers Count	Single Lib Directory (Recursive)	2.16x faster	equal
Tool Importers Count	Entire Lib Directory (Non-Recursive)	1.43x faster	equal
Tool Importers Count	Entire Lib Directory (Recursive)	1.09x faster	equal
Tool Importers	Global Lib File	2.67x faster	equal
Tool Importers	Single Env-Specific Lib File	1.67x faster	equal
Tool Importers	All Env-Specific Lib Files	6.9x faster	equal
Tool Importers	All Lib Files	6.61x faster	equal
Tool Importers	All Jsonnet Files	11.68x faster	equal
Tool Imports	Single Static Environment	3.29x faster	equal
Tool Imports	Single Inline Environment File	3.34x faster	equal

Full results available in workflow artifacts.

Benchmark run on commit 4b0afff677a8273c595f654588374e02f15af2af