fix(ego-browser): recover help() from live helpers when docs are empty

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Summary

help() still returns Unknown helper for every helper on the shipped ego lite 0.4.6.14 app. Recover a usable signature from the live helper function when the embedded docs catalog is empty or missing that name.

Related issue

Closes #287

Related: #84, #85, #273

Changes

• When help() has no names and the embedded catalog is empty, list live helpers from the current helper context.
• When help(name) misses an embedded doc, recover the signature from the live function instead of immediately returning Unknown helper.
• Keep Unknown helper only for names that are not present as live functions.
• Add regression tests for an empty catalog, a missing-but-live helper, and a truly unknown name.

Verification

cd package/ego-browser
CI=true npm ci
npm test
# 314 pass, 0 fail

Local 0.4.6.14 app still reproduces the empty catalog:

ego-browser nodejs <<'EOF'
cliLog(help('click'))
cliLog(typeof click)
EOF
# Unknown helper: click
# function

This PR does not patch the closed-source app binary. It makes the next runtime ship degrade to live signatures instead of an empty catalog.

Impact

• Public helper API or behavior
• Agent skill or instructions
• Site learning
• Installation or update flow
• Build, CI, or release process
• Documentation only
• No externally visible impact

help() remains the same public function. Agents that currently get an empty string / Unknown helper will get recovered signatures when the helper exists. True unknown names are unchanged.

Checklist

• The PR targets the correct base branch (dev for normal changes; only dev may target main).
• The change is focused and does not include unrelated cleanup.
• Tests were added or updated for behavior changes, or the reason they are unnecessary is explained above.
• Relevant tests and validation commands pass locally.
• Public helper JSDoc and agent-facing documentation are updated when the helper surface changes.
• No credentials, tokens, cookies, personal data, or other secrets are included.
• A release-note label is selected (feat, fix, docs, chore, ci, or refactor).