fix(sim): two rules of one kind on one asset get a row each (#829)

[eaitbrahim]

Closes #829.

What was wrong

report.edge_table and report.accumulation_table (#825) keyed each row "{rule.name}:{asset}". When two rules of the same kind sit on the same asset, the later rule's row overwrote the earlier one's.

• On the deployment: ~/keel/keel.db has two paper BTC DCA rules, rule 19 at $50/week and rule 20 at $5/week. keel simulate printed a single row, the $5 rule's, which looked like a ~$5/week DCA. The $50 sleeve was invisible.
• A second, quieter effect: group_trades_by_class looked both rules up by that shared key. G2's per-class pool counted the surviving rule's trades twice and the other rule's not at all. The test below shows a class pool of 0 trades where the pooled row has 1. The pooled row itself was always right, because it extends every rule's trades before keying.

The fix

One function, report.rule_keys(rules), now keys all three tables:

• A key that is already unique is unchanged ("turtle_breakout:BTC"), so existing readers and tests are untouched.
• Rules that share a key are told apart by their rules.id ("dca#19:BTC", "dca#20:BTC"), or by position when a hand-built rule has no id. No row is ever lost.
• All three tables must be given the same rules list, which simulate already does. The docstrings say so.

Verification

• tests/sim/test_rule_keys.py has 6 tests. Five failed first on the old code; the "unique key unchanged" test is a regression pin that passes throughout. They cover:

  • two DCA rules, each at its own budget
  • two edge rules on one asset, with correct pooled N
  • the class pool counting each rule once (it was 0, now 1)
  • unique keys unchanged
  • colliding rules without ids
  • the rendered section showing both rows

• Five mutants were each checked to have changed the source, and each was killed:

  Mutant	Tests failed
  never disambiguate	5
  class pool uses the old key	1
  accumulation uses the old key	2
  always disambiguate	12
  ignore rule_id	3

• Real data, on a copy of the paper database over the 5-year window:

  Row	Buys	Cost	Value
  dca#19:BTC	261	$13,213.14 ($50.63/buy)	$25,715.00
  dca#20:BTC	261	$1,321.31 ($5.06/buy)	$2,571.50

  Before the fix only the second row printed.

• Full suite: 6775 passed, 3 skipped. mypy, ruff check and ruff format --check are clean.

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