Replace site tour with Achievements + secret Easter eggs

[GLAXYIAS]

Summary

Removes the broken driver.js site tour and replaces it with an Achievements system.

Changes

• achievements.js (new): modal UI, progress badge, localStorage unlocks (nx_achievements), toast notifications
• tour.js: no longer runs a tour — bootstraps achievements and renames the old Site Tour button to Achievements (so index.html does not need a full rewrite)

Achievements

Normal (description shown while locked):

• Welcome Aboard, Trophy Case, Boot Sequence, Collector, Feeling Lucky, System Preferences, Ghost Protocol, Comms Online, Identity Check, Bypass Engineer, Query Runner

Easter eggs (locked = ??? + vague hint only — never says where/how):

• Classic Input, Persistent Clicker, Night Shift, Under the Hood, Triple Tap, Archive Diver, Follow the White Rabbit

Notes

• Progress is browser-local only
• Secrets stay cryptic until unlocked; hints do not spoil the exact trigger
• Optional follow-up: point index.html at achievements.js directly and delete the tour CDN script for a cleaner load

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