Adds the foundation layer for Puppeteer-parity features:
- TabSession.loadedHtml + setTabContent/getLoadedHtml/clearLoadedHtml —
enables load-html content to survive context recreation (viewport --scale)
via in-memory replay. ASCII lifecycle diagram in the source explains the
clear-before-navigation contract.
- COMMAND_ALIASES + canonicalizeCommand() helper — single source of truth
for name aliases (setcontent / set-content / setContent → load-html),
consumed by server dispatch and chain prevalidation.
- buildUnknownCommandError() pure function — rich error messages with
Levenshtein-based "Did you mean" suggestions (distance ≤ 2, input
length ≥ 4 to skip 2-letter noise) and NEW_IN_VERSION upgrade hints.
- load-html registered in WRITE_COMMANDS + SCOPE_WRITE so scoped write
tokens can use it.
- screenshot and viewport descriptions updated for upcoming flags.
- New browse/test/dx-polish.test.ts (15 tests): alias canonicalization,
Levenshtein threshold + alphabetical tiebreak, short-input guard,
NEW_IN_VERSION upgrade hint, alias + scope integration invariants.
No consumers yet — pure additive foundation. Safe to bisect on its own.
