Add missing duration flag to Bladefall, Smoke Mine and Cold Snap

[lemmertz]

Fixes #5125 .

Description of the problem being solved:

Dread Banner and War Banner (the original report) already received the duration flag in #9559. A comment in this issue listed other skills with the same problem. Of those, Bladefall, Bladefall of Trarthus, Smoke Mine and Cold Snap still have a base skill effect duration but no duration base flag, so their Skill Duration was hidden in the Calcs tab.

Ethereal Knives, Shattering Steel and Cyclone no longer have a duration in the current game data, so they are left unchanged.

Both the export scripts (src/Export/Skills) and the generated data (src/Data/Skills) were updated.

Steps taken to verify a working solution:

• Tested on dev (v2.67.2, based on commit 16de4b8), Windows 11
• Created a new build with Cold Snap, Bladefall and Smoke Mine
• Checked the Calcs tab: Skill Duration is now shown (Cold Snap 5.016s, Bladefall 6.006s, Smoke Mine 5.016s + Secondary Duration 1.023s)
• Damage values are unchanged; the flag only affects which stats are displayed

Link to a build that showcases this PR:

N/A

Before screenshot:

Skill Duration row missing in Calcs tab

After screenshot:

(screenshots attached in a comment below)

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AI disclosure: the investigation and code changes were made with Claude Code (model: Claude Opus 5.5, claude-opus-5-5); testing in the app and screenshots were done by me.

🤖 Generated with Claude Code

[lemmertz]

Before / After screenshots

Cold Snap — before:

after:

Bladefall — before:

after:

Smoke Mine — before:

after: