changelog: document unreleased changes since 15.1.0

[bhavishyaa-sahuu]

Summary

Fills in the TBD section of CHANGELOG.md for commits already on master since 15.1.0 that are user-facing:

Entry	Source
aarch64-unknown-linux-musl tests/artifacts	Fixes #2739 (48a6ad9)
Parent gitignore matching across multi-root walks	Fixes #3419 (43e2f08 / #3420)
container file type (Dockerfile / Containerfile)	#3271 (9b84e15)
hurl file type	#3444 (dfe4a81)
Existing: skip .jj stat under --no-ignore	#3212 (85edf4c) — already listed

Docs-only / internal / CI-test commits (AI policy, GUIDE lexopt wording, QEMU cmd_exists, crate renames, etc.) intentionally omitted to match prior changelog practice.

Context for reviewers / handoff

This continues interrupted release-prep work in a local checkout of BurntSushi/ripgrep at dfe4a81 (in sync with origin/master).

Not in this PR (and not on disk anymore): earlier experimental sessions implemented (1) an internal search-execution telemetry framework and (2) library API cleanups (globset 0.5 / ignore 0.5 deprecations). Those were discarded under a release-risk-minimization pass; only this changelog documentation remained as durable local work. There is no open PR for telemetry or those API bumps.

GitHub checks performed: no open/draft/merged PR already documents this TBD batch; remote CHANGELOG.md on master still only lists #3212 under TBD.

Test plan

• Diff entries against git log since 36b7597 (start of TBD section)
• Cross-check issue/PR numbers via GitHub API (states closed/merged as expected)
• Confirm master tip matches origin/master / GitHub dfe4a81
• Maintainer review of wording / categorization only (no code changes)