Fixdecision insertion inside html comment

[doguhanniltextra]

Problem

On a fresh DECISIONS.md scaffolded by ctx init, running ctx add decision inserts the new entry inside the <!-- DECISION FORMATS ... --> comment block, making it invisible when rendered in any Markdown viewer.

Issue

#10

The INDEX table at the top updates correctly, but the decision body is hidden — users don't notice until they view the rendered page.

Root cause

Two bugs in internal/cli/add/insert.go:

1. insertDecision used strings.Index(content, "## [") which matched the ## [YYYY-MM-DD] Decision Title template example that lives inside the <!-- DECISION FORMATS ... --> comment block.

2. insertAfterHeader (the fallback path when no real entries exist yet) only skipped <!-- ctx:context --> and <!-- ctx:end --> markers. It stopped at <!-- INDEX:START --> and inserted before the index table and format-guide comment.

Fix

• isInsideHTMLComment(content, idx) — new helper that checks whether a byte position falls between a <!-- and its closing -->.
• insertDecision / insertLearning — rewritten to walk all ## [ occurrences in a loop, skipping any that isInsideHTMLComment identifies as being inside a comment block.
• insertAfterHeader — updated to skip any <!-- ... --> block (not just ctx-specific markers), so the fallback path clears the INDEX markers and the DECISION FORMATS guide before placing the insertion point.

Tests

• TestInsertDecisionNotInsideComment — regression test using the exact fresh-file structure from the bug report, with two sub-tests:
  • first decision lands after the comment block
  • second decision prepends correctly before the first (order preserved)
• TestIsInsideHTMLComment — 8 table-driven unit tests for the new helper, covering: before/inside/after a comment, inline single-line comment, multi-line comment with heading inside vs after close, unclosed comment, and no-comment content.

All existing tests in internal/cli/add continue to pass.

Checklist

• go fmt ./internal/cli/add/... — clean
• go vet ./internal/cli/add/... — clean
• go test ./internal/cli/add/... -count=1 — all pass
• Regression test added (TestInsertDecisionNotInsideComment)
• Unit test added for new helper (TestIsInsideHTMLComment)
• DCO sign-off on all commits