infra: reproducible build + signed release pipeline

Adds the infrastructure for verifiable Triangles releases:
- Reproducible builds (default-on): -ffile-prefix-map strips absolute
  source paths from binaries; SOURCE_DATE_EPOCH pinned to commit
  timestamp if env var not set. Two builds of the same commit with the
  same flags now produce byte-identical binaries.
- scripts/verify-reproducible-build.sh: builds the daemon twice into
  separate build dirs and compares SHA256. Pass/fail printed clearly.
- scripts/sign-release.sh: generates SHA256SUMS, writes detached .asc
  signatures over each release artifact and over SHA256SUMS itself.
  Supports --verify for independent third-party verification.
- release-process.md: canonical release pipeline documentation --
  reproducibility properties, signing-key setup, distribution
  requirements, failure-mode recovery, and the release checklist.
- scripts/README.md: updated to catalog the full scripts/ directory
  (was previously scoped only to bump-version.sh).

Verified end-to-end on this branch:
- scripts/verify-reproducible-build.sh: exit 0, both builds SHA256
  7a86d9659b7150f69dc53eb31cc4c7eb8df296b55fa889af5c5a1b310223c894.
- scripts/sign-release.sh: signs Release-built artifact, --verify
  returns exit 0 (all sigs + checksums valid).
- ctest: 4/4 suites still pass with the new compile flags.
- Tamper test: modifying an artifact after signing causes --verify
  to fail with '1 checksum(s) FAILED' (exit 1).

Existing signing key in the local keyring is used:
  523A81833EB7201573E1EFE1DCF2579968107984
  (Krystie Triangles Release <krystie-triangles-release@dns2.sami.tailnet>)

CI integration (separate PR): add a 'sign' job to build-all.yml that
imports GPG_PRIVATE_KEY from secrets and runs scripts/sign-release.sh
against the assembled release directory. Documented in release-process.md.

scripts/README.md

@@ -1,29 +1,36 @@
-# Version Bump Script
+# Scripts
 
-Updates the version number across all files in the repo from a single command.
+Operational scripts for the Triangles project. See also `release-process.md`
+at the repo root for the canonical release pipeline documentation.
 
-## Usage
+## Build verification
 
-**Set a specific version:**
-```bash
-bash scripts/bump-version.sh 5.7.0
-```
+- **`verify-reproducible-build.sh`** — builds the daemon (or another target)
+  twice from the same source tree and verifies the SHA256 hashes match.
+  Catches accidental introduction of non-determinism (e.g. `__DATE__`/`__TIME__`
+  regressions, dirty git state, PIE base-address drift).
 
-**Or edit `src/clientversion.h` first, then sync everything else:**
-```bash
-bash scripts/bump-version.sh
-```
+## Release signing
 
-## What it updates
+- **`sign-release.sh`** — generates `SHA256SUMS`, writes detached PGP
+  signatures (`.asc`) over each release artifact and over `SHA256SUMS`.
+  Supports `--verify` for independent third-party verification.
+  Uses `TRIANGLES_RELEASE_KEY` env var (defaults to
+  `sami@cryptographic-triangles.org`).
 
-- `src/clientversion.h` (source of truth)
-- `src/version.h`
-- `triangles-qt.pro`
-- `Dockerfile`
-- All packaging manifests (Docker, Snap, Scoop, WinGet, RPM, Flatpak, Debian, AppImage)
+## Existing infrastructure
 
-## What still needs manual review after running
-
-- `packaging/appstream/...metainfo.xml` — add a new `<release>` entry
-- `README.md` — update header version if desired
-- Any documentation with download URLs
+- **`bump-version.sh`** — sync version numbers across all manifests from
+  `src/clientversion.h`.
+- **`sign-snapshot.sh`** — sign a UTXO snapshot file with the wallet's
+  signing address (not a PGP key; this is a chain-level signature, not a
+  release signature).
+- **`validate_onion_seeds.py`** — validate every `.onion` address in
+  `triangles.conf` against the v3 hidden-service checksum.
+- **`ibd-smoke-test.sh`** — fresh-datadir IBD smoke test for catching the
+  classic "stalls early / loops around 570" failure mode.
+- **`ci/build-rocksdb.sh`** — build and install a pinned RocksDB version
+  for CI.
+- **`ci/package-linux-daemon.sh`** — Linux packaging step (.deb).
+- **`ci/package-windows-daemon.sh`** — Windows packaging step.
+- **`tri/`** — operator-facing CLI for node administration.