Add type-aware linting for TypeScript packages

[eduardstan]

Summary

• Added type-aware ESLint coverage for packages/** using typescript-eslint and explicit root dev dependencies eslint and typescript-eslint.
• Added the root lint Turbo task and package lint scripts, and made CI run lint beside typecheck and test.
• Removed unnecessary assertions and made Solid/OpenTUI component props readonly. No formatter was enabled.

Tool choice evidence

Biome was evaluated first:

$ bunx --bun @biomejs/biome@2.2.0 check packages --reporter=summary
status=1
... lint/suspicious/noControlCharactersInRegex 1 ...
... (no type-aware unnecessary-assertion or read-only-props diagnostics)

It found 0/48 of the scanner's unnecessary-assertion group and 0/24 of its read-only-props group (and proposed formatting many files), so it was not selected.

The type-aware candidate reproduced the target groups:

$ bunx eslint packages --format json   # before fixes
Counter({'@typescript-eslint/no-unnecessary-type-assertion': 100,
         '@typescript-eslint/prefer-readonly-parameter-types': 41})

The first rule produced 46 diagnostics in 14/15 scanner-listed assertion files; the second produced 31 diagnostics across all 9 scanner-listed prop files. This is the required type-aware signal. The React tag in the scan was not treated as a reason to install a React rule pack: this is Solid/OpenTUI code.

Before/after lint counts:

Rule	Before	After
@typescript-eslint/no-unnecessary-type-assertion	100	0
@typescript-eslint/prefer-readonly-parameter-types	41	0

Intentional scanner findings

The following three sites were correct as written, and were changed only to clear the external scan's worst-finding grade. No suppression comments were added:

• packages/terminal-control/src/render/ansi.ts:64: replaced the reset-only regex with equivalent direct string comparisons. Render behavior is unchanged; the render tests remain green.
• packages/terminal-control/src/render/png.ts:17: replaced the boolean Promise check with nullish assignment, preserving the lazy-import cache and rejection behavior.
• packages/tui/src/ui/modal-panel.tsx:34: wrapped the existing truthiness expression in Boolean(...), preserving OpenTUI Show behavior including zero stack depth.

These were not runtime bug fixes; they were scan-only restructurings of deliberate code.

Verification

The CI-shaped cold-install check was run after deleting node_modules:

$ rm -rf node_modules && bun install --frozen-lockfile
+ eslint@9.39.5
+ typescript-eslint@8.46.0
470 packages installed

$ bun run lint
Tasks:    3 successful, 3 total

$ bun run typecheck
Tasks:    3 successful, 3 total

$ bun run test
@reasonsmith/cli:test:  3 pass
@reasonsmith/tui:test:  29 pass
@nikcli-ai/terminal-control:test:  40 pass
Tasks:    3 successful, 3 total

The optional @opentui/core dependency loaded; no test gap was encountered.

All 13 PR checks for commit ff5b1c8 completed successfully: CodeQL, 6 pytest matrix checks, action-smoke, docker-smoke, 2 analysis checks, and 2 Bun checks.