feat(scanner): reject non-standard plugin JSON constants

[seonghobae]

Current repair boundary — 2026-09-12

• base: feat/claude-plugin-deceptive-description-1099@df1ba2c3207478393a7fc797470558ad028d931d
• exact head: b02bfdecec575edf593a72388df2cd749afdf204
• exact tree: ed9943cd3321b1c8349b825b3a49bfa8775b03a4
• ancestry: ordinary two-parent merge of previous feat(scanner): reject non-standard plugin JSON constants #1153 head 3f709b0… and current feat(scanner): reject deceptive plugin capability descriptions #1151 head df1ba2c…; no force update
• exact-tree validation: PYTHONPATH=. python -m pytest -q tests/test_claude_plugin*.py → 173 passed; py_compile and git diff --check passed
• lifecycle: Draft / non-standard JSON delta and all parent repairs preserved / hosted exact-head Checks and independent review absent
• stacked-workflow admission remains owned by fix(ci): admit stacked PR checks without bypassing docs contracts #1096; do not create a source-neutral wake-up commit

Successor of #1151 / issue #1099. Does not Close those. Does not steal G-06 #1152, #1151 deceptive-description, or #1150 browser-profile unique delta. Duplicate JSON members stay claude-plugin-duplicate-json-member.

Unique delta

Fail closed on non-standard JSON constants (claude-plugin-nonstandard-json-constant):

• plugin.json timeout: NaN fails admission
• Infinity and -Infinity fail admission
• a finite JSON number is not this finding
• duplicate object members stay claude-plugin-duplicate-json-member
• README text is not a manifest
• truncated JSON is a parse failure, not this class
• feat(scanner): reject deceptive plugin capability descriptions #1151 deceptive descriptions stay that class
• snippets are the constant token and omit secrets and raw bidi

#1151 remains owner of deceptive plugin/skill/command descriptions.

Test plan

• RED then GREEN (tests/test_claude_plugin_nonstandard_json.py)
• Detector statement coverage 1576/1576 with plugin suites on Python 3.13
• Exact-head Checks on this head
• Keep Draft until current-head gates are GREEN

Relates to #1099. Relates to #1151.

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[seonghobae]

Stacked successor: #1154 (feat/claude-plugin-malformed-utf8-1099 @ ee43e7d).

It owns the remaining issue #1099 TDD item 4 malformed UTF-8/Unicode slice (claude-plugin-malformed-utf8). It does not Close #1099 or this PR. Bidi/control stays claude-plugin-concealed-identity. Duplicate members stay #1129. Non-standard JSON constants stay this PR.