feat(cfl): port space key in page view/search

[rianjs]

Port space key display improvements from confluence-cli PR #104.

Files to modify:

• tools/cfl/api/search.go - Extract space key from search results
• tools/cfl/internal/cmd/page/view.go - Display space key
• tools/cfl/internal/cmd/search/search.go - Add SPACE KEY column
• Tests for each

Features:

page view:

• Table/plain: Display space key alongside space ID (e.g., Space: DEV (ID: 9999))
• JSON: Enrich with spaceKey field via GetSpace API call

search:

• Add SPACE KEY column from resultGlobalContainer.displayUrl

Graceful fallback if space lookup fails.

Source: open-cli-collective/confluence-cli#104

[rianjs]

Implementation Plan

1. page view - Add space key display

• Add SpaceID field to Page struct if not already present (it is - checking)
• After fetching page, call GetSpace(spaceID) to get space key
• Display as Space: DEV (ID: 9999) in table/plain output
• For JSON output, enrich the page object with spaceKey field
• Graceful fallback: if GetSpace fails, just show space ID

2. search - Add SPACE KEY column

• Add helper function to extract space key from resultGlobalContainer.displayUrl
  • URL format: /spaces/SPACEKEY/... or /wiki/spaces/SPACEKEY/...
• Change headers from ["ID", "TYPE", "SPACE", "TITLE"] to ["ID", "TYPE", "SPACE KEY", "TITLE"]
• Extract space key from displayUrl instead of using space title

3. Tests

• Test page view with space key lookup
• Test page view graceful fallback when space lookup fails
• Test search space key extraction from displayUrl
• Table-driven tests for extractSpaceKey helper