add --require-spec to check-prerequisites

[HuzaifaChaudary]

Closes #4364

problem

check-prerequisites validates FEATURE_DIR, plan.md, and tasks.md under --require-tasks, each with an error naming the command to run. it resolves FEATURE_SPEC, exports it in the json payload and prints it in text mode, but never checks that the file exists.

analyze and converge both call it and then read spec.md directly. with the spec missing the prerequisite check exits 0, and the failure surfaces later without the "run specify first" guidance the script gives for everything else, which is the thing this script exists to prevent.

fix

a --require-spec flag, shaped exactly like --require-tasks:

ERROR: spec.md not found in specs/001-my-feature
Run /speckit.specify first to create the feature specification.

it is opt in, as suggested in the issue, so nothing changes for callers that do not read the spec. analyze and converge pass it because they do.

all three variants

the flag is in bash, powershell and python. that is not gold plating, the parity tests compare help text, json output and error shapes across the three, so adding it to one would have broken them.

file	change
scripts/bash/check-prerequisites.sh	--require-spec
scripts/powershell/check-prerequisites.ps1	-RequireSpec
scripts/python/check_prerequisites.py	--require-spec
templates/commands/analyze.md	passes the flag, sh and ps
templates/commands/converge.md	passes the flag, sh and ps

tests

test_python_require_spec_matches_bash covers three states across bash and python:

• spec missing and no flag, both exit 0, so the opt in stays opt in
• spec missing with the flag, both exit 1 with byte identical stderr
• spec present with the flag, both exit 0 with identical json

it fails on main with ERROR: Unknown option '--require-spec'.

verification

check	result
new test on main	fails
new test with the change	passes
full suite before	10 failed, 7135 passed
full suite after	10 failed, 7137 passed
new failures introduced	none, i diffed the two failure lists
ruff check scripts tests	all checks passed

the 10 pre existing failures are the composed template parity tests and are unrelated to this.

---

disclaimer: this contribution was prepared with the assistance of an ai agent. i reproduced the gap first, checked which callers actually read the spec, and ran the parity suite locally before opening this.

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