fix: stabilize with statement formatting with comments

[todor-a]

Fixes #787.

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Transparency note: This PR was prepared with AI assistance (Claude).

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Problem

with (a) { //
}

emits Error formatting repro.ts. Message: Formatting not stable. Bailed after 5 tries.

Root cause

Node::WithStmt had no IR generator. It fell into the gen_node_inner fallback at the bottom of the dispatch (Class | Function | Invalid | WithStmt | TsModuleBlock), which calls gen_from_raw_string(node.text_fast(...)) — i.e. emits the original source bytes verbatim without walking children.

That bypasses the comment tracker. The inner // is never marked consumed, so on the next pass it's re-emitted as a trailing comment after the closing brace. Each format pass appends another //:

with (a) { //   →   with (a) { //   →   with (a) { //
}                   } //                } //
                                        //

Stability check bails after 5 attempts.

Fix

Add a real gen_with_stmt mirroring gen_while_stmt. with (obj) body has the same shape as while (test) body (keyword + parenthesized expression + body statement), so the new function reuses the existing while_statement_* configuration rather than introducing new config keys (with is deprecated and forbidden in strict mode, so dedicated config seems unwarranted).

Removed WithStmt from the "should never be matched" fallback list.

Tests

Added tests for this specific case, plus extra tests from https://github.com/prettier/prettier/tree/main/tests/format/json/with-comment.