Fix prettier↔eslint config drift on comma-dangle functions

[senoff]

Original Problem

.prettierrc had "trailingComma": "all", which adds trailing commas after function parameters and arguments. .eslintrc had "comma-dangle": functions: "never". Running prettier then eslint (or vice versa) produces changes each tool immediately reverts. The conflict caused pre-commit hook failures on any PR that ran prettier's format step. See the three concurrent PRs (#58, #59) that each independently included .prettierrc changes because the hook was fighting them.

Cause

trailingComma: "all" is a Prettier setting introduced in Prettier 2 that adds commas in function signatures. ESLint's comma-dangle: { functions: "never" } is the inverse. The two configs were set independently and neither was updated when the other changed.

Fix

Change .prettierrc to "trailingComma": "es5" — this stops prettier from adding trailing commas in function calls/definitions, which is the only location where eslint and prettier disagreed.

Four supporting .eslintrc changes that reduce false-positive lint errors arising from prettier's formatting:

• import/extensions: off — CommonJS require() project; import extension enforcement is irrelevant.
• max-len: ignoreTemplateLiterals: true — template literals can legitimately exceed 120 chars; prettier does not break them.
• quotes: avoidEscape: true — allows double quotes when the string contains single quotes; prettier uses this heuristic.
• space-before-function-paren: anonymous: "ignore" — prettier formats anonymous functions without a space; "never" caused lint errors on valid prettier output.

Files changed

• .prettierrc — "trailingComma" value changed from "all" to "es5"
• .eslintrc — four rule adjustments

Test Run

No code changed — config only. Pre-commit hook conflict reduced: with trailingComma: "es5" prettier no longer writes trailing commas in function calls, so eslint's comma-dangle: functions: "never" is satisfied.

Cross-PR check

PRs #58 and #59 both include .prettierrc edits (same change: "all" → "es5"). Their regenerated versions will strip that .prettierrc edit and reference this PR as the canonical config change. No other open PRs touch .eslintrc or .prettierrc.

Excel/soffice verification

Not applicable — config only, no XLSX serialization touched.

grace-review summary

openai:gpt-5.5 — No defects found. gemini:gemini-2.5-flash — MEDIUM: import/extensions: off concern; LOW: anonymous spacing. Both dismissed: this is a Node.js CommonJS project (require()-only), import/extensions is irrelevant. Anonymous spacing set to "ignore" because prettier's output varies and "never" was generating false-positive errors on valid code.

Note: committed with --no-verify per AGENTS.md Rule 1 (pre-commit hook conflict is the exact problem this PR fixes).