Add EMTA KMD draft tooling and harden EMTA/LHV session persistence

[TonisOrmisson]

This PR adds KMD support to emta-cli so agents can list declarations, read draft data, update the KMD main form, read/
update/delete INF A and INF B rows, and use a separate guarded submit command. It also hardens EMTA/LHV session handling
for WSL/Linux by adding file-based fallback session storage and updating the current EMTA govsso + customer-kmd2 flow.
Main changes:

• Added emta-cli kmd list
• Added emta-cli kmd main create|read|update
• Added emta-cli kmd inf-a read|update|delete
• Added emta-cli kmd inf-b read|update|delete
• Added guarded emta-cli kmd submit --confirm
• Added file-session fallback for EMTA and LHV when keyring/secrets is unavailable
• Added parser/merge/session tests
• Sanitized tests/examples and added repo instruction forbidding real private data in tracked files/history
• Updated GitHub Actions runtimes and branch-push workflow triggers

Validation:

• go test ./... passes in cli/emta
• go test ./internal/config passes in cli/lhv
• Live-tested against EMTA KMD draft workflow
• Live-tested KMD main save, INF A update/delete, INF B validation path, and declaration submit flow

Notes:

• JSON is the default machine-readable input/output format for the new KMD commands
• submit remains a separate explicit command because users may want to review saved drafts before final submission

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[stefanoamorelli]

nit: I appreciate those improvements but maybe worth another PR to keep diff cleaner? WDYT?

[stefanoamorelli]

blocking: I think this change deserves more conversation as we're changing from encrypted keychain to plaintext storage of the credentials.

IMHO worth discussing in more detail on another issue and PR.

[stefanoamorelli]

thanks a lot @TonisOrmisson! Really appreciate the kmd implementation. I left a couple of comments, overall if we could scope down this PR just for the kmd feature to avoid mix of concerns it would be fantastic.