Make portable position lookup and close respect canonical symbol case #116

Affected version: 0.1.2; public main 43fc66f. Environment: Python 3.12, offline provider transports.

Observed behavior: The position lookup uses the caller's lowercase spelling and leaves the uppercase position open.

Expected behavior and acceptance: After a public shadow order creates an AAPL position, get_position('aapl') and close_position_async('aapl') must find and close that position. The strategy wrapper must behave consistently. Paper lookup must use the same canonical symbol.

Verify a public API or feed workflow fails against the unchanged producing base and passes with the repair. Record exact revisions and commands, run the applicable full quality gates, and preserve failure atomicity. No live-money orders or release actions.

This focused issue owns one repair originally reported in #111 and proposed in #112. Retain the original contributor's attribution. The bundled report remains open until all five independent problems are substantively resolved.

AI assistance: Codex prepared this focused maintenance issue from the existing report.