docs(project): INTRO.md and AGENTS.md secret-purge record

- INTRO.md: plain-English project overview with Erdős #336 rationale
- AGENTS.md: document secret purge (Postgres, Porkbun, DeepSeek, 4 others)
  and key rotation across all 3 repos

6-Documentation/docs/INTRO.md

@@ -0,0 +1,145 @@
+# Research Stack — Plain English Intro
+
+Proto-concept December 2025, initial concept February 2026. This document is the 5-minute version.
+
+---
+
+## What is this, really?
+
+A machine that takes a hard puzzle and **chews on it until the answer falls out**.
+
+The twist: every step is double-checked by a computer program (Lean) that
+mathematically proves the answer is correct. No guesswork. No "we think this
+works." The computer can't cheat.
+
+---
+
+## How it works (3 steps)
+
+### Step 1: Give the puzzle to 8 conveyor belts
+
+Take any puzzle — a Sudoku grid, a compression task, a physics equation,
+a math problem.
+
+Slice the puzzle into 8 parallel streams of data. Each stream runs down its
+own conveyor belt, and each belt gets a unique **barcode**: one of the numbers
+`1, 2, 4, 8, 16, 32, 64, 128`.
+
+These barcodes are special: because they're powers of 2, you can add any two
+and get a unique third number (3 = 1+2, but no other pair sums to 3). This
+means every crossing of two belts leaves a trace that can't be faked.
+
+### Step 2: Merge the belts until they stop changing
+
+The 8 belts feed into each other in pairs. Every time two belts meet, they:
+- Add their data together
+- XOR their barcodes to produce a new crossing ID
+- Record how much they changed (the "residual")
+
+This repeats in a loop. Each pass merges the strands, records the changes,
+and feeds the result back in.
+
+Eventually the belts **stop changing**. A pass produces the same data as the
+pass before. That stable state is called an **eigensolid** — think of it as
+a coiled spring that has finished settling.
+
+### Step 3: Read the receipt
+
+The final state is a **receipt** with six numbers:
+- Which barcodes crossed (the "crossing matrix")
+- How much barcode budget is left (the "Sidon slack")
+- How many merge passes it took
+- The complete history of residuals
+- A timestamp
+- A flag saying "no errors occurred"
+
+That receipt IS the answer. For compression: the receipt is the compressed
+file. For a math proof: the receipt replaces pages of algebra.
+
+The computer can reverse the receipt back into the original puzzle, proving
+nothing was lost.
+
+---
+
+## "This sounds like a normal algorithm, what's special?"
+
+Three things:
+
+### No rounding errors
+
+The math uses **fixed-point numbers** (like counting pennies instead of dollars
+with decimals). Every chip in the world — GPU, FPGA, CPU, phone, ASIC —
+computes these numbers the same way. There is no "it works on my machine."
+
+If this runs on a graphics card or a custom chip or an Arduino, the answer is
+identical.
+
+### No cheating
+
+Every step is written in the Lean language. Lean is a proof checker: it is
+impossible to write an incorrect proof and have Lean accept it. If the code
+compiles, the math is right.
+
+### The answer is a barcode, not a number
+
+Instead of saying "the answer is 42," the system produces a **structural
+barcode** that captures the shape of the solution. This matters because two
+different puzzles with the same structure produce the same barcode — which is
+how the system discovers hidden connections between unrelated things.
+
+---
+
+## What has it actually done?
+
+- **8 theorems** proven in Lean about the braid reaching a stable state
+- **250 math equations** classified by structural type
+- A compression receipt system verified in formal logic
+- FPGA hardware extraction (runs on $7 dev boards)
+- Connection between compression and astronomy data (DESI)
+- Connection between math proofs and Sudoku solvers
+
+---
+
+## Why Erdős Problem #336?
+
+It's the test case that validates the whole pipeline in one small package.
+
+The problem asks: can you build a set of numbers where the *order* (the
+minimum number of terms needed to represent any large enough integer) is 2,
+but the *exact order* (the minimum number that actually works for every
+integer) is 3? Erdős found such a set — a union of intervals based on powers
+of two.
+
+This one problem hits every stress point the pipeline needs to survive:
+
+| What it tests | Why it matters |
+|---------------|---------------|
+| **Implied infinities** | The set is infinite; the encoder must truncate it and reconstruct the tail. |
+| **Two conflicting answers** | Order=2 and exact order=3 must coexist in the same layout without contradiction. |
+| **Cross-domain constraint chain** | The exact-order proof depends on a coprime-number theorem — propagation must fire across multiple constraint types. |
+| **Reverse verification** | After encoding and cycling to a stable state, decoding must recover the original set and both numbers. |
+| **Barcode uniqueness** | The truncated set must have distinct crossing sums (Sidon injectivity). |
+| **Deep structure, tiny input** | Only 3 intervals (8 numbers), but encodes an infinite construction pattern. |
+
+Passing #336 means the pipeline handles infinities, contradictory-looking
+constraints, theorem coupling, lossless round-trip, and barcode integrity —
+all at once. If it passes this, it passes almost anything.
+
+---
+
+## Where to start reading
+
+Not this document — go deeper:
+
+| File | What it is |
+|------|-----------|
+| `AGENTS.md` | The full operating manual for the project |
+| `0-Core-Formalism/lean/` | The Lean formal proofs (ground truth) |
+| `4-Infrastructure/` | Hardware + driver code |
+| `6-Documentation/docs/` | Design docs, receipts, spec sheets |
+| `shared-data/` | Generated data and artifacts |
+
+---
+
+*This project has no corporate sponsor, no grant funding, and no team. It is a
+single person's attempt to find the universal shape of an answer.*

AGENTS.md

@@ -669,6 +669,49 @@ Problem via TSP-MTZ) and benchmarks against the QUBO subset-selection approach a
 - `/tmp/finsler_benchmark_v3.json` — n=8,12,24 results (structued JSON)
 - `/tmp/finsler_benchmark_n48.json` — n=48 results
 
+## Secret Purge & Key Rotation (2026-06-28)
+
+A full secret purge was performed across all 3 public GitHub repos after secrets
+were found in git history and tracked files.
+
+### What was removed from git
+
+| Secret | File/History | Fix |
+|--------|-------------|-----|
+| PostgreSQL password | `service_orchestrator.py` | Changed from hardcoded URL to `os.environ["DATABASE_URL"]` |
+| Porkbun API key + secret | `porkbun.env` (tracked in distributed-compute-fabric) | `git rm --cached`, added to `.gitignore` |
+| DeepSeek API key | `deploy.sh` + git history (all 3 repos) | Replaced with `os.environ.get()`, history rewritten |
+| Quandela API key | `deploy.sh` | Replaced with `os.environ.get()` |
+| Wolfram Alpha API key | `deploy.sh` | Replaced with `os.environ.get()` |
+| Linear API key | `deploy.sh` | Replaced with `os.environ.get()` |
+| Bedrock API key | `deploy.sh` | Replaced with `os.environ.get()` |
+
+### Method
+
+- `git filter-repo --replace-text` on all 3 repos with literal secret patterns
+- Force-pushed to GitHub (Research Stack, distributed-compute-fabric, research-compute-fabric)
+- Hardcoded API keys in `deploy.sh` replaced with env var reads; script now sources
+  `.env` file for local development
+
+### Key rotation
+
+- **Porkbun**: Old keys revoked at porkbun.com, new pair generated (stored in
+  `4-Infrastructure/deploy/credential-server/.env`, gitignored)
+- **DeepSeek**: User provided new key `sk-b84c...` (stored in same `.env`)
+
+### New/modified files this session
+
+| File | Status | Purpose |
+|------|--------|---------|
+| `6-Documentation/docs/INTRO.md` | Untracked | Plain-English project intro with Erdős #336 rationale |
+| `4-Infrastructure/deploy/credential-server/deploy.sh` | Modified (gitignored) | Added `.env` sourcing for secret injection |
+| `4-Infrastructure/deploy/credential-server/.env` | New (gitignored) | Local secrets (Porkbun, DeepSeek) |
+
+### Still pending
+
+- Push rewritten history to Forgejo (`git.researchstack.info:30022` — service currently down)
+- Set rotated keys in runtime environments (shell rc, systemd units, etc.)
+
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