bug(build): --cfg flag skipped on incremental no-op — requires --no-incremental for first CFG build

[carlos-alm]

Found during dogfooding v2.6.32-dev.4f08082

Severity: Medium
Command: codegraph build . --cfg

Reproduction

# Build without --cfg first
codegraph build . --no-incremental
# Now add --cfg
codegraph build . --cfg --verbose

Expected behavior

The --cfg flag should trigger CFG computation even when no files have changed, since this is the first time CFG data is being requested.

Actual behavior

Output: "No changes detected. Graph is up to date." — CFG data is NOT computed. All cfg queries return 0 blocks and 0 edges.

Running build . --cfg --no-incremental works correctly (887 functions analyzed for CFG).

Root cause

The incremental build detects no file changes and short-circuits before the CFG computation phase. The --cfg and --dataflow flags should force re-processing even when the file content hasn't changed, similar to how --no-incremental forces a full rebuild.

Suggested fix

When --cfg or --dataflow is passed and the corresponding data doesn't exist in the DB yet, skip the "no changes detected" early return and proceed with the computation phase.

[carlos-alm]

Fixed in #293