pin flatc version and regenerate stale code

[Shane98c]

Fixes CI error on #7

Two issues fixed:

1. Stale generated code (broke CI): Upstream schema changes (new node_id/node_type fields on MoveOperation) were pulled in by prepare > sync-flatbuffers.sh but the generated TypeScript was never regenerated, so check:fbs failed.

2. No pinned flatc version (latent risk): CI installed one flatc version, local dev could use another. This didn't cause the current failure, but would cause hard-to-debug diffs if versions ever produced different output for the same schema.

Fix:

• Regenerate TypeScript to match current upstream schemas
• Add scripts/ensure-flatc.sh which pins flatc v25.12.19, auto-downloads to .bin/ if missing
• generate:fbs and check:fbs npm scripts use the pinned version
• Remove manual flatc install step from CI (the script handles it)

[gemini-code-assist]

Code Review

This pull request implements a pinned flatc compiler versioning system to ensure consistent FlatBuffers code generation across different environments. It adds a script to automatically download the required binary, updates the project's build scripts, and includes updated generated TypeScript files. The review feedback focuses on enhancing the shell script's portability and reliability through better dependency checking and error handling, as well as ensuring a clean state during the FlatBuffers verification process.

[gemini-code-assist]

Using #!/usr/bin/env bash is more portable than #!/bin/bash, as it avoids hardcoding the path to the bash executable which may vary across different Unix-like systems.

Suggested change

	#!/bin/bash
	#!/usr/bin/env bash

[gemini-code-assist]

It's recommended to verify that the required tools (curl and unzip) are available before proceeding with the download and extraction process to provide a clearer error message if they are missing.

Suggested change

	set -euo pipefail
	set -euo pipefail
	# Check dependencies
	for cmd in curl unzip; do
	if ! command -v "$cmd" >/dev/null 2>&1; then
	echo "error: $cmd is required but not installed." >&2
	exit 1
	fi
	done

[gemini-code-assist]

Adding the -f flag to curl ensures the script fails if the download returns an HTTP error code (like 404). Additionally, consider verifying the checksum of the downloaded binary to ensure its integrity and security.

Suggested change

	curl -sL "$URL" -o "$TMPDIR/flatc.zip"
	curl -fsSL "$URL" -o "$TMPDIR/flatc.zip"

[gemini-code-assist]

Cleaning the /tmp/fbs-check directory before running flatc ensures that the comparison is performed against a fresh set of generated files, preventing false positives from stale files left over from previous runs.

Suggested change

	"check:fbs": "FLATC=\"$(./scripts/ensure-flatc.sh)\" && \"$FLATC\" -T -o /tmp/fbs-check --gen-all ./flatbuffers/all.fbs && node scripts/postgen-fbs.cjs /tmp/fbs-check && prettier --write /tmp/fbs-check/generated && diff -r /tmp/fbs-check/generated src/format/flatbuffers/generated"
	"check:fbs": "rm -rf /tmp/fbs-check && mkdir -p /tmp/fbs-check && FLATC=\"$(./scripts/ensure-flatc.sh)\" && \"$FLATC\" -T -o /tmp/fbs-check --gen-all ./flatbuffers/all.fbs && node scripts/postgen-fbs.cjs /tmp/fbs-check && prettier --write /tmp/fbs-check/generated && diff -r /tmp/fbs-check/generated src/format/flatbuffers/generated"