Graduate experimental features to default

[Iron-Ham]

Summary

• Ship 5 experimental features as always-on defaults: intelligent naming, terminal support, inline multiplan, inline ultraplan, and grouped instance view
• Remove config struct fields, viper registrations, feature gates, disabled-state tests, and TUI config editor entries for graduated features
• Only subprocess_mode remains experimental
• Clean up stale triple_shot references from documentation
• Update all docs (README, configuration guide, inline planning guide, keyboard shortcuts, TUI navigation)

Details

Config layer: Removed 5 fields from ExperimentalConfig, keeping only SubprocessMode. Updated defaults and viper registration.

Gate removal: Removed isTerminalEnabled(), terminalDisabledError, and all conditional checks in command handlers (cmdTerminal, cmdTerminalFocus, cmdTerminalDirWorktree, cmdTerminalDirProject, cmdMultiPlan, cmdUltraPlan), key handlers (handleToggleTerminal, handleSwitchTerminalDir), and orchestrator (initNamer).

Intelligent naming: IntelligentNamingEnabled() now always returns true. The namer still requires ANTHROPIC_API_KEY — the config gate was just an additional opt-in that's no longer needed.

Tests: Removed TestTerminalCommandsDisabled, TestTerminalKeybindingsDisabled, TestHandleNormalModeKeyTerminalDisabled, and "disabled by default" subtests from multiplan/ultraplan test suites. Removed all viper.Set("experimental.*") enablement calls from remaining tests.

Net result: -468 lines, +32 lines. Removes viper imports from 4 files.

Test plan

• go build ./... passes
• go test -race ./... passes (only pre-existing golangci-lint toolchain mismatch)
• go vet ./... clean
• gofmt -d . clean
• TestTUIConfigCoversAllConfigFields confirms config struct/TUI editor sync
• Deep review: no P0 issues, one P1 (stale triple_shot refs) fixed