[FEAT] Implement Phase 1: gatherers, audits, and runner pipeline (#38)

[IISweetHeartII]

Description

Implements the complete Phase 1 Gather → Audit → Score pipeline, making @agentgram/ax-score a fully functional CLI tool and library. Previously, runAudit() returned an empty report with score 0. Now it performs real network fetches, analyzes 19 signals, and produces actionable scores.

Type of Change

• New feature (non-breaking change which adds functionality)

Changes Made

Gatherers (3 new files)

• HttpGatherer (src/gatherers/http-gatherer.ts): Fetches target URL + 6 well-known files in parallel (robots.txt, llms.txt, openapi.json, ai-plugin.json, sitemap.xml, security.txt)
• HtmlGatherer (src/gatherers/html-gatherer.ts): Regex-based extraction of JSON-LD, meta tags, semantic HTML elements, links (zero external dependencies)
• ApiGatherer (src/gatherers/api-gatherer.ts): Analyzes OpenAPI spec validity, response headers, auth patterns, rate limiting, SDK availability

Audits (19 new files)

Category	Audits	Weight
Discovery	llms-txt, openapi-spec, robots-ai, ai-plugin, schema-org	25%
API Quality	openapi-valid, response-format, response-examples, content-negotiation	25%
Structured Data	json-ld, meta-tags, semantic-html	20%
Auth & Onboarding	self-service-auth, no-captcha	15%
Error Handling	error-codes, rate-limit-headers, retry-after	10%
Documentation	machine-readable-docs, sdk-available	5%

Runner Pipeline

• Two-pass gathering: HTTP (network) → HTML + API (derived)
• All 19 audits execute in parallel with error resilience
• Failed audits score 0 without crashing the pipeline
• Results feed into existing scoring engine (weighted arithmetic mean)

Updated Exports

• src/index.ts: Exports concrete gatherer classes and types
• src/audits/index.ts: Exports all 19 audit classes
• src/gatherers/index.ts: Exports all 3 gatherer classes

Smoke Test Result

$ ax-score https://agentgram.co
AX Score: 89/100 ██████████████████░░
[PASS] Discovery         100/25
[WARN] API Quality        88/25
[PASS] Structured Data   100/20
[WARN] Auth & Onboarding  67/15
[WARN] Error Handling      70/10
[PASS] Documentation     100/5

Related Issues

Closes #38

Testing

• Manual testing performed (agentgram.co → 89/100)
• Type check passes (pnpm type-check)
• Lint passes (pnpm lint)
• Build succeeds (pnpm build)

Checklist

• My code follows the project's code style
• I have performed a self-review of my code
• My changes generate no new warnings
• No external dependencies added (uses native fetch + regex)

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