Add astral community ability

community/astral/README.md

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+# Astral — deterministic base capability
+![Community](https://img.shields.io/badge/OpenHome-Community-orange?style=flat-square)
+![Skill](https://img.shields.io/badge/Category-Skill-green?style=flat-square)
+
+Instant answers for the things with one right answer: time, date, math, money, unit conversions, grades, chemistry, physics, statistics, and number tools. Computed directly, no model. Anything else passes to your agent.
+
+This is the generalized version of the `date-and-time` base capability. The whole engine is inlined in `main.py` (pattern and table code, no `eval`), so it runs anywhere an agent runs, no DevKit required.
+
+## Category
+
+**Skill.** Trigger words route a phrase here; the engine answers and the agent handles the rest.
+
+## What it answers
+
+- Time and date, in the agent's timezone.
+- Math: add, subtract, multiply, divide, percentages, powers, roots, factorials.
+- Money: tips, tax, splitting a bill.
+- Unit conversions: weight, length, volume, temperature, speed, area, time, energy,
+  pressure, force, data sizes, and astronomical distances.
+- Grades: what you need on the final, weighted totals, percent to letter, score out of
+  total, GPA over credits.
+- Chemistry: molar mass for a named compound or a formula, moles and grams, molarity,
+  pH, the ideal gas law, atomic mass and number for all 118 elements.
+- Physics: escape velocity and surface gravity for the Sun, the Moon and every planet,
+  weight on another world, free fall, kinetic and potential energy, momentum, force,
+  work, power, Ohm's law, time dilation, Schwarzschild radius, photon energy, light
+  travel time.
+- Statistics: mean, median, mode, range, variance, sample and population standard
+  deviation, z scores, combinations and permutations.
+- Number tools: binary, hex and octal, logs, trig, GCD and LCM, primes and prime
+  factors, modulo, the quadratic formula, percent change, fractions, significant
+  figures, scientific notation.
+
+Examples:
+
+```
+what time is it                    -> It's 3:55 pm.
+what's twenty percent of eighty     -> 20 percent of 80 is 16.
+convert ten pounds to kilograms     -> 10 pounds is 4.54 kilograms.
+eighteen percent tip on forty five dollars
+                                    -> A tip of 18 percent on 45 dollars is 8.1 dollars, for a total of 53.1.
+I have an 87 and the final is worth 20 percent, what do I need to get a 90
+                                    -> You'd need 102 percent on the final for 90 percent,
+                                       which isn't possible. A perfect final leaves you at 89.6 percent.
+molar mass of water                 -> The molar mass of water (H2O) is 18.015 grams per mole.
+escape velocity of mars             -> Escape velocity at Mars is 5.02 kilometers per second,
+                                       11234.25 miles per hour.
+standard deviation of 4 6 8 10      -> The sample standard deviation of 4, 6, 8, 10 is 2.58,
+                                       around a mean of 7.
+is 91 prime                         -> No, 91 isn't prime. It's 7 times 13.
+tell me a joke                       -> (nothing; the agent takes it)
+```
+
+Two things it says out loud rather than assuming. Anything resting on a grading scale
+names the scale, because a scale is a convention and not a fact. A standard deviation
+says whether it is the sample or the population one, because those are different numbers
+and a course grades you on which you used.
+
+## Suggested trigger words
+
+Set these in the dashboard:
+
+`what time`, `what's the time`, `what's the date`, `what day is it`, `calculate`, `what's`, `how much is`, `percent of`, `square root of`, `convert`, `how many`, `tip on`, `tax on`, `split`, `what do i need`, `what letter grade`, `out of`, `weighted`, `gpa`, `molar mass`, `how many moles`, `atomic mass`, `atomic number`, `molarity`, `ph of`, `escape velocity`, `surface gravity`, `kinetic energy`, `momentum`, `how long does light`, `average of`, `mean of`, `median of`, `standard deviation`, `z score`, `choose`, `in binary`, `in hexadecimal`, `log of`, `sine of`, `prime factors`, `quadratic`, `percent change`, `simplify`, `significant figures`
+
+## How it works
+
+`main.py` is a `MatchingCapability`. On a trigger word it takes the transcript, normalizes the punctuation, routes it through the inlined engine, and speaks the answer. The engine is one router with a fixed order: time and date first, then grades, chemistry, physics, statistics, number tools, and plain arithmetic last. Specific before general, because the general one will match a fragment of a specific question. If nothing matches, it speaks nothing and calls `resume_normal_flow()` so the agent takes the turn. Never blocks, never blanket-denies.
+
+## Accuracy
+
+Every answer is a formula over a table, so it is either exactly right or it does not
+answer. Unit factors are the exact defined values. Molar masses are computed by parsing
+the formula against the element table rather than stored per compound, because a
+hand-entered constant is a typo waiting to be spoken with confidence. Surface gravity
+and escape velocity are computed from mass and equatorial radius and agree with
+published figures for eight bodies to better than half a percent.
+
+120 answers are asserted byte-exact in the source repo, alongside a suite that fuzzes
+four thousand utterances and rechecks every result a second independent way — statistics
+against Python's own `statistics` module, factorizations multiplied back out, physics
+against published constants.
+
+## Requirements
+
+Python standard library only. No API keys, no external services.
+
+## Note
+
+This version computes in the cloud, without the LLM. For the fully on-device, no-network path (wake and speech-to-text on the DevKit too), see the local DevKit build.