Keep the plan summary working for outputs-only plans

[gsavage]

Addresses #33

Problem

The Plan summary step in .github/workflows/base.yml grepped the saved plan for No changes. or
Plan: and assigned the match to a variable. GitHub Actions runs run: blocks under bash -e, so
when neither pattern was present grep exited 1 and failed the whole job.

Terraform prints neither of those lines when a plan changes only outputs — it prints
Changes to Outputs: — so any change that adds or edits an output without touching resources broke
the plan workflow for callers, as seen in
capture-managed.

Change

Tolerate a non-matching grep, falling back to the Changes to Outputs: header and then to a generic
message pointing at the uploaded plan. The plan path is hoisted into a variable so the later
grep -q shares it.

has_changes is unchanged in meaning: an outputs-only plan has no No changes. line, so it still
reports true and the apply job still runs.

Testing

Ran the patched block under bash -e against four sample plan files:

plan content	summary	has_changes
Changes to Outputs: only	Changes to Outputs:	true
No changes. Your infrastructure matches…	that line	false
Plan: 1 to add, 0 to change, 0 to destroy.	that line	true
unrecognised output	See the uploaded plan for details.	true

No case exits non-zero. The workflow file still parses as YAML.

The Apply summary step has the same shape, but Apply complete! is printed on every successful
apply, so it is left alone.