Add JSON output format to aegisctl pending

[saivedant169]

Problem

aegisctl pending currently prints a human-readable table. That is great for people, but it is painful to parse in scripts or CI.

Acceptance criteria

• Adding --json to aegisctl pending prints the raw JSON array from the admin API
• The default (no flag) still prints the table
• Exit code is 0 when there are pending items, 0 when there are none
• A unit test covers the JSON path in cmd/aegisctl/

Files to touch

• cmd/aegisctl/main.go (the pending command handler)
• Add a test file if one does not exist for this command

How to test locally

Start AegisFlow with a review-path rule, trigger a review, then:

./bin/aegisctl pending --json
# Expected: a JSON array, parseable with jq
./bin/aegisctl pending --json | jq '.[0].envelope.tool'

Notes

If you want to do the same for aegisctl approve, deny, and evidence export, that is welcome but please open a separate PR per command so each one is reviewable.