fix(cli): consumer-found DX fixes for chat, .env, doctor and eval

[LinuxDevil]

Problem

A consumer run of the CLI found:

1. lousho chat printed only error: User not found. (an OpenRouter 401), dropping the error code, category, HTTP status and fix that docs/cli.md promises. The scaffolded src/index.ts had the same issue.
2. A .env saved with a UTF-8 BOM (PowerShell 5.1 Set-Content -Encoding utf8) silently lost its first key: process.loadEnvFile keeps the BOM, so the variable came out as \uFEFFOPENROUTER_API_KEY.
3. lousho doctor: doctor src/agent.ts failed with LOUSHO_SPEC_UNSUPPORTED_FORMAT and the wrong fix text. The scaffold's npm run doctor (no path) exited 0 with the agent's key missing. --ping passed with a bogus OpenRouter key because /models needs no auth. Fix lines said export X= on Windows.
4. The lousho eval table hid the scores of passing scored gates; they only showed up in --json.
5. fallow dead-code reported two false positives in packages/create-lousho-agent.
6. On Windows, npx C:\abs\path\x.tgz silently does nothing, and the docs didn't say so.

Fix

• chat REPL: error events are held until the run ends. The error that failed the run is printed from the run's rejection: error: <msg> (<category>, HTTP <status>), then [CODE] hint (docs). Other error events print with their code's help line. The scaffold's errorText does the same through the public SDKError API.
• .env: bin/lousho.js and the scaffold read the file, strip a leading BOM and parse it with util.parseEnv (Node >= 21.7; the engines floor is 22.19). Variables already set still win.
• doctor: .ts/.js modules are imported the same way lousho dev imports them (new agentModuleConfig() in devReload; the agent is not built). The doctor checks the module's model provider, so a missing key is a failure. The scaffold's doctor script is now lousho doctor src/agent.ts. OpenRouter is pinged at /api/v1/key, a 401/403 is a failure, and a custom OPENAI_BASE_URL ping is labelled reachability-only. Fix lines use $env:X="..." on win32. An unsupported file type gets the right fix text.
• eval: the SCORES column shows every assertion that isn't a plain yes/no (0/1 against threshold 1).
• .fallowrc.json: added ignoreUnresolvedImports for ../dist/index.js and ignoreExports for create-lousho-agent's main.
• Docs: cli.md, installation.md, the create-lousho-agent README, CHANGELOG Unreleased, llms-full.txt.

Verification

• Tests written first: chat (provider 401 printed once, with category, status and code), bin (BOM .env, existing env wins), doctorCore (module loading, missing key fails, OpenRouter /key, reachability label, PowerShell fix, unsupported-format fix), templates, evalReport.
• npx tsc --noEmit, npm run lint, npm run docs:llms:check and npm run build pass. npx vitest run src/cli passes: 536 tests.
• packages/create-lousho-agent template e2e (real install, typecheck, tests) passes with the new template.
• Manual Windows run: lousho doctor agent.ts with a BOM .env loads the key from .env, loads the module, FAILs on the missing OpenRouter key with a PowerShell fix line, and exits 1.
• npx fallow dead-code: the two create-lousho-agent findings are gone. Still reported, and unrelated to this PR: @lousho/build-ai-agent as an unused dependency of apps/agent-forge. It looks specific to this worktree.
• Full npm run test:coverage on Windows: 1 failure, the timing-sensitive src/storage/sqlite/connection.test.ts lock-contention test. It passes on its own (env-only, under load). Because of that failure no coverage file was written, so the full npm run fallow health run did not happen locally.

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