burn(docs): Add JSDoc comments to key LIR lowering functions

[bkmashiro]

Task

• ID: 01KNHZFNWDAP2PPQ7AFK4980F5
• Type: docs
• Priority: 1
• CLI: claude

Description

In src/lir/lower.ts, add JSDoc block comments to the following functions that currently have no documentation: lowerFunction(), lowerInstr(), lowerTerminator(), operandToSlot(), and constSlot(). Each JSDoc should explain: what the function does, its parameters, return value, and any notable side effects (e.g. when new instructions or temporary slots are emitted as a result). Also add a comment on the MAX_ITERATIONS = 20 constant in src/optimizer/pipeline.ts explaining that it is the fixpoint iteration cap for the optimizer pass pipeline.

Changes

src/lir/lower.ts          | 85 +++++++++++++++++++++++++++++++++++++++++++++--
 src/optimizer/pipeline.ts |  3 ++
 2 files changed, 86 insertions(+), 2 deletions(-)

---

Generated by burn-harness