Reconcile NPC names

[alixthegreat]

Two NPCs were renamed in their game scenarios to resolve accidental cross-scenario name overlaps. This PR updates all source files (ink dialogue, scenario config, documentation) so that display names are consistent throughout. NPC id fields are intentionally left unchanged to preserve audio cache resolution.

SIS02 Energy — SCADA Engineer renamed from Priya Chandra → Helen Marsh. Updated across scenario.json.erb, npc_helen_marsh.ink (renamed from npc_priya_chandra.ink), npc_marcus_webb.ink, information_pack.md, TESTING_WALKTHROUGH.md, TODO.md, VALIDATION_SUMMARY.md, and INK_DEVELOPMENT_SUMMARY.md. Variable/task-id renames (priya_briefed → helen_briefed, talk_to_priya → talk_to_helen) coordinated between the ink file and scenario.json.erb. Dr Priya Sharma (NCSC inspector) references are untouched.

SIS03 Cyber Insurance — Loss adjuster renamed from David Osei → Simon Hartley. The in-game implementation already used Simon Hartley; this commit updates information_pack.md (11 occurrences) and VALIDATION_SUMMARY.md (1 occurrence) to match. The osei_report_envelope object ID is intentionally left unchanged.

[alixthegreat]

I realised there are also inconsistencies in scenario 2 with Dr Bashir needing to be fully renamed to Priya Sharma so I will complete this first. Also need to fix issue where this npc doesn't appear after all task completions and I can't trigger the debrief / scenario completion.

[cliffe]

Ok -- let me know once it's ready to merge

[alixthegreat]

Ready to merge now. Renamed Dr Bashir to Priya Sharma throughout. Fixed spawn issue: facility_safe_state and priya_sharma_visible are now set directly from Tom Hadley's Ink, bypassing the conditions which were silently failing due to the evaluator not supporting globalVars.* syntax.