Add LSF scheduler (parser + emitter)

[stackedsax]

Add support for IBM Spectrum LSF (#BSUB scripts), the other remaining planned HPC scheduler. Community-validated (IBM license needed for a live cluster).

Scope

• internal/parser/lsf — #BSUB directives → SPLAT
• internal/emitter/lsf — SPLAT → #BSUB script
• Register in both all/all.go; drop from the "Planned" list in cmd/bammm/main.go; mark ✅ in the README table

Notes

• Directive-style parser like Slurm/PBS (see those for the pattern)
• Priority via -sp; add a PriorityScale
• Preserve unmapped #BSUB options in extensions.lsf

Process: follow docs/adding-a-scheduler.md. Validation is Tier 1/2 locally; Tier 3 needs a contributor with an LSF cluster.