[APPS][Connections Part 7] Add reusable module graph walker

[sdkennedy2]

Motivation

Split the reusable module graph traversal helper out from the connection ID extraction PR so reviewers can evaluate the graph-walking behavior independently.

Changes

This PR adds walkModuleGraph, a small backend AST parsing helper that walks collected app-local module records from a backend entry module. The helper owns reachability mechanics only: it visits each reachable collected module once, follows parseable app-local static dependencies, and fails closed when the collected graph is incomplete or contains unsupported local dependency facts.

For example, a later connection ID consumer can use the helper to collect IDs from every reachable module without reimplementing graph traversal:

const connectionIds = new Set<string>();

walkModuleGraph(entryId, moduleRecords, buildRoot, ({ moduleId, record }) => {
    for (const connectionId of extractConnectionIds(record.ast, moduleId)) {
        connectionIds.add(connectionId);
    }
});

return [...connectionIds].sort();

The helper deliberately does not know about action-catalog calls, connection ID values, Vite collectors, manifests, or dev-server execution. Those behaviors remain in the next PR in the stack.

QA Instructions

Added focused unit coverage for reachability traversal, cycle handling, dependency skip rules, and fail-closed graph gaps. Also ran the apps plugin typecheck and scoped lint coverage for the new helper.

Blast Radius

This adds a reusable internal helper under backend/ast-parsing. It is not wired into production or dev execution until the next PR consumes it.

Documentation

• PR Description Guidelines

[sdkennedy2]

• [APPS][Connections Part 8] Traverse backend module graph for connection IDs #362 : 2 dependent PRs (#363 , #365 )
• [APPS][Connections Part 7] Add reusable module graph walker #364 👈 (View in Graphite)
• [APPS][Connections Part 6] Build backend module graph during backend builds #353
• [APPS][Connections Part 5] Move apps Vite behavior into getVitePlugin #357
• [APPS][Connections Part 4] Resolve same-module connection ID object values #354
• [APPS][Connections Part 3] Resolve same-module connection ID constants #351
• master

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[sdkennedy2]

@codex review
@cursor review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. You're on a roll.

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[sarenji]

Non-blocker, is it possible to use ensureProgram here? Or no?

[sdkennedy2]

Good call. 👍